SQL: Implement sorting and retrieving score (elastic/x-pack-elasticsearch#3340)

Accessing `_score` from SQL looks like:
```
--------------------------------------------------
POST /_sql
{
    "query": "SELECT SCORE(), * FROM library WHERE match(name, 'dune') ORDER BY SCORE() DESC"
}
--------------------------------------------------
```

This replaces elastic/x-pack-elasticsearch#3187

relates elastic/x-pack-elasticsearch#2887

Original commit: elastic/x-pack-elasticsearch@fe96348c22

docs/build.gradle

@@ -213,8 +213,14 @@ setups['library'] = '''
               book:
                 properties:
                   name:
+                    type: text
+                    fields:
+                      keyword:
                         type: keyword
                   author:
+                    type: text
+                    fields:
+                      keyword:
                         type: keyword
                   release_date:
                     type: date
@@ -232,6 +238,12 @@ setups['library'] = '''
             {"name": "Hyperion", "author": "Dan Simmons", "release_date": "1989-05-26", "page_count": 482}
             {"index":{"_id": "Dune"}}
             {"name": "Dune", "author": "Frank Herbert", "release_date": "1965-06-01", "page_count": 604}
+            {"index":{"_id": "Dune Messiah"}}
+            {"name": "Dune Messiah", "author": "Frank Herbert", "release_date": "1969-10-15", "page_count": 331}
+            {"index":{"_id": "Children of Dune"}}
+            {"name": "Children of Dune", "author": "Frank Herbert", "release_date": "1976-04-21", "page_count": 408}
+            {"index":{"_id": "God Emperor of Dune"}}
+            {"name": "God Emperor of Dune", "author": "Frank Herbert", "release_date": "1981-05-28", "page_count": 454}
             {"index":{"_id": "Consider Phlebas"}}
             {"name": "Consider Phlebas", "author": "Iain M. Banks", "release_date": "1987-04-23", "page_count": 471}
             {"index":{"_id": "Pandora's Star"}}

docs/en/sql/endpoints/sql-rest.asciidoc

@@ -28,6 +28,7 @@ Frank Herbert    |Dune                |604            |-144720000000
 Alastair Reynolds|Revelation Space    |585            |953078400000
 James S.A. Corey |Leviathan Wakes     |561            |1306972800000
 --------------------------------------------------
+// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/]
 // TESTRESPONSE[_cat]
 
 You can also choose to get results in a structured format by adding the `format` parameter. Currently supported formats:
@@ -58,8 +59,8 @@ Which returns:
 --------------------------------------------------
 {
     "columns": [
-        {"name": "author",       "type": "keyword"},
+        {"name": "author",       "type": "text"},
-        {"name": "name",         "type": "keyword"},
+        {"name": "name",         "type": "text"},
         {"name": "page_count",   "type": "short"},
         {"name": "release_date", "type": "date"}
     ],
@@ -100,8 +101,8 @@ Which looks like:
         ["Dan Simmons",        "Hyperion",             482,  612144000000],
         ["Iain M. Banks",      "Consider Phlebas",     471,  546134400000],
         ["Neal Stephenson",    "Snow Crash",           470,  707356800000],
-        ["Robert A. Heinlein", "Starship Troopers",    335, -318297600000],
+        ["Frank Herbert",      "God Emperor of Dune",  454,  359856000000],
-        ["George Orwell",      "1984",                 328,  486432000000]
+        ["Frank Herbert",      "Children of Dune",     408,  198892800000]
     ],
     "cursor" : "sDXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAAEWODRMaXBUaVlRN21iTlRyWHZWYUdrdw==:BAFmBmF1dGhvcgFmBG5hbWUBZgpwYWdlX2NvdW50AWYMcmVsZWFzZV9kYXRl9f///w8="
 }
@@ -174,6 +175,7 @@ Which returns:
 ---------------+------------------------------------+---------------+---------------
 Douglas Adams  |The Hitchhiker's Guide to the Galaxy|180            |308534400000
 --------------------------------------------------
+// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/]
 // TESTRESPONSE[_cat]
 
 [[sql-rest-fields]]

docs/en/sql/endpoints/sql-translate.asciidoc

@@ -23,11 +23,16 @@ Which returns:
 {
     "size" : 10,
     "docvalue_fields" : [
-        "author",
-        "name",
         "page_count",
         "release_date"
     ],
+    "_source": {
+        "includes": [
+            "author",
+            "name"
+        ],
+        "excludes": []
+    },
     "sort" : [
         {
             "page_count" : {

docs/en/sql/language/sql-syntax.asciidoc

@@ -9,3 +9,92 @@ Each entry might get its own file and code snippet
 --------------------------------------------------
 include-tagged::{sql-spec}/select.sql-spec[wildcardWithOrder]
 --------------------------------------------------
+
+
+[[sql-spec-syntax-order-by]]
+==== ORDER BY
+
+Elasticsearch supports `ORDER BY` for consistent ordering. You add
+any field in the index that has <<doc-values,`doc_values`>> or
+`SCORE()` to sort by `_score`. By default SQL sorts on what it
+considers to be the most efficient way to get the results.
+
+So sorting by a field looks like:
+
+[source,js]
+--------------------------------------------------
+POST /_xpack/sql
+{
+    "query": "SELECT * FROM library ORDER BY page_count DESC LIMIT 5"
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:library]
+
+which results in something like:
+
+[source,text]
+--------------------------------------------------
+     author      |        name        |  page_count   | release_date
+-----------------+--------------------+---------------+---------------
+Peter F. Hamilton|Pandora's Star      |768            |1078185600000
+Vernor Vinge     |A Fire Upon the Deep|613            |707356800000
+Frank Herbert    |Dune                |604            |-144720000000
+Alastair Reynolds|Revelation Space    |585            |953078400000
+James S.A. Corey |Leviathan Wakes     |561            |1306972800000
+--------------------------------------------------
+// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/]
+// TESTRESPONSE[_cat]
+
+[[sql-spec-syntax-order-by-score]]
+For sorting by score to be meaningful you need to include a full
+text query in the `WHERE` clause. For example:
+
+[source,js]
+--------------------------------------------------
+POST /_xpack/sql
+{
+    "query": "SELECT SCORE(), * FROM library WHERE match(name, 'dune') ORDER BY SCORE() DESC"
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:library]
+
+Which results in something like:
+
+[source,text]
+--------------------------------------------------
+    SCORE()    |    author     |       name        |  page_count   | release_date
+---------------+---------------+-------------------+---------------+---------------
+2.288635       |Frank Herbert  |Dune               |604            |-144720000000
+1.8893257      |Frank Herbert  |Dune Messiah       |331            |-6739200000
+1.6086555      |Frank Herbert  |Children of Dune   |408            |198892800000
+1.4005898      |Frank Herbert  |God Emperor of Dune|454            |359856000000
+--------------------------------------------------
+// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/ s/\(/\\\(/ s/\)/\\\)/]
+// TESTRESPONSE[_cat]
+
+Note that you can return `SCORE()` by adding it to the where clause. This
+is possible even if you are not sorting by `SCORE()`:
+
+[source,js]
+--------------------------------------------------
+POST /_xpack/sql
+{
+    "query": "SELECT SCORE(), * FROM library WHERE match(name, 'dune') ORDER BY page_count DESC"
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:library]
+
+[source,text]
+--------------------------------------------------
+    SCORE()    |    author     |       name        |  page_count   | release_date
+---------------+---------------+-------------------+---------------+---------------
+2.288635       |Frank Herbert  |Dune               |604            |-144720000000
+1.4005898      |Frank Herbert  |God Emperor of Dune|454            |359856000000
+1.6086555      |Frank Herbert  |Children of Dune   |408            |198892800000
+1.8893257      |Frank Herbert  |Dune Messiah       |331            |-6739200000
+--------------------------------------------------
+// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/ s/\(/\\\(/ s/\)/\\\)/]
+// TESTRESPONSE[_cat]

qa/sql/no-security/src/test/java/org/elasticsearch/xpack/qa/sql/nosecurity/CliExplainIT.java

@@ -45,7 +45,14 @@ public class CliExplainIT extends CliIntegrationTestCase {
         assertThat(readLine(), startsWith("      \"test_field\""));
         assertThat(readLine(), startsWith("    ],"));
         assertThat(readLine(), startsWith("    \"excludes\" : [ ]"));
+        assertThat(readLine(), startsWith("  },"));
+        assertThat(readLine(), startsWith("  \"sort\" : ["));
+        assertThat(readLine(), startsWith("    {"));
+        assertThat(readLine(), startsWith("      \"_doc\" :"));
+        assertThat(readLine(), startsWith("        \"order\" : \"asc\""));
         assertThat(readLine(), startsWith("      }"));
+        assertThat(readLine(), startsWith("    }"));
+        assertThat(readLine(), startsWith("  ]"));
         assertThat(readLine(), startsWith("}]"));
         assertEquals("", readLine());
     }
@@ -97,6 +104,13 @@ public class CliExplainIT extends CliIntegrationTestCase {
         assertThat(readLine(), startsWith("  },"));
         assertThat(readLine(), startsWith("  \"docvalue_fields\" : ["));
         assertThat(readLine(), startsWith("    \"i\""));
+        assertThat(readLine(), startsWith("  ],"));
+        assertThat(readLine(), startsWith("  \"sort\" : ["));
+        assertThat(readLine(), startsWith("    {"));
+        assertThat(readLine(), startsWith("      \"_doc\" :"));
+        assertThat(readLine(), startsWith("        \"order\" : \"asc\""));
+        assertThat(readLine(), startsWith("      }"));
+        assertThat(readLine(), startsWith("    }"));
         assertThat(readLine(), startsWith("  ]"));
         assertThat(readLine(), startsWith("}]"));
         assertEquals("", readLine());
@@ -132,7 +146,14 @@ public class CliExplainIT extends CliIntegrationTestCase {
         assertThat(readLine(), startsWith("EsQueryExec[test,{"));
         assertThat(readLine(), startsWith("  \"size\" : 0,"));
         assertThat(readLine(), startsWith("  \"_source\" : false,"));
-        assertThat(readLine(), startsWith("  \"stored_fields\" : \"_none_\""));
+        assertThat(readLine(), startsWith("  \"stored_fields\" : \"_none_\","));
+        assertThat(readLine(), startsWith("  \"sort\" : ["));
+        assertThat(readLine(), startsWith("    {"));
+        assertThat(readLine(), startsWith("      \"_doc\" :"));
+        assertThat(readLine(), startsWith("        \"order\" : \"asc\""));
+        assertThat(readLine(), startsWith("      }"));
+        assertThat(readLine(), startsWith("    }"));
+        assertThat(readLine(), startsWith("  ]"));
         assertThat(readLine(), startsWith("}]"));
         assertEquals("", readLine());
     }

qa/sql/src/main/java/org/elasticsearch/xpack/qa/sql/ErrorsTestCase.java

@@ -16,4 +16,9 @@ public interface ErrorsTestCase {
     void testSelectFromIndexWithoutTypes() throws Exception;
     void testSelectMissingField() throws Exception;
     void testSelectMissingFunction() throws Exception;
+    void testSelectProjectScoreInAggContext() throws Exception;
+    void testSelectOrderByScoreInAggContext() throws Exception;
+    void testSelectGroupByScore() throws Exception;
+    void testSelectScoreSubField() throws Exception;
+    void testSelectScoreInScalar() throws Exception;
 }

qa/sql/src/main/java/org/elasticsearch/xpack/qa/sql/cli/ErrorsTestCase.java

@@ -11,6 +11,8 @@ import org.apache.http.entity.StringEntity;
 
 import static java.util.Collections.emptyMap;
 
+import static org.hamcrest.Matchers.startsWith;
+
 /**
  * Tests for error messages.
  */
@@ -49,4 +51,42 @@ public abstract class ErrorsTestCase extends CliIntegrationTestCase implements o
         assertEquals("[1;31mBad request [[22;3;33mFound 1 problem(s)", command("SELECT missing(foo) FROM test"));
         assertEquals("line 1:8: Unknown function [missing][1;23;31m][0m", readLine());
     }
+
+    @Override
+    public void testSelectProjectScoreInAggContext() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        assertEquals("[1;31mBad request [[22;3;33mFound 1 problem(s)", command("SELECT foo, SCORE(), COUNT(*) FROM test GROUP BY foo"));
+        assertEquals("line 1:13: Cannot use non-grouped column [SCORE()], expected [foo][1;23;31m][0m", readLine());
+    }
+
+    @Override
+    public void testSelectOrderByScoreInAggContext() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        assertEquals("[1;31mBad request [[22;3;33mFound 1 problem(s)",
+            command("SELECT foo, COUNT(*) FROM test GROUP BY foo ORDER BY SCORE()"));
+        assertEquals("line 1:54: Cannot order by non-grouped column [SCORE()], expected [foo][1;23;31m][0m", readLine());
+    }
+
+    @Override
+    public void testSelectGroupByScore() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        assertEquals("[1;31mBad request [[22;3;33mFound 1 problem(s)",
+            command("SELECT COUNT(*) FROM test GROUP BY SCORE()"));
+        assertEquals("line 1:36: Cannot use [SCORE()] for grouping[1;23;31m][0m", readLine());
+    }
+
+    @Override
+    public void testSelectScoreSubField() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        assertThat(command("SELECT SCORE().bar FROM test"),
+            startsWith("[1;31mBad request [[22;3;33mline 1:15: extraneous input '.' expecting {<EOF>, ',',"));
+    }
+
+    @Override
+    public void testSelectScoreInScalar() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        assertEquals("[1;31mBad request [[22;3;33mFound 1 problem(s)",
+            command("SELECT SIN(SCORE()) FROM test"));
+        assertEquals("line 1:12: [SCORE()] cannot be an argument to a function[1;23;31m][0m", readLine());
+    }
 }

qa/sql/src/main/java/org/elasticsearch/xpack/qa/sql/cli/ShowTestCase.java

@@ -39,7 +39,8 @@ public abstract class ShowTestCase extends CliIntegrationTestCase {
         while (scalarFunction.matcher(line).matches()) {
             line = readLine();
         }
-        assertEquals("", line);
+        assertThat(line, RegexMatcher.matches("\\s*SCORE\\s*\\|\\s*SCORE\\s*"));
+        assertEquals("", readLine());
     }
 
     public void testShowFunctionsLikePrefix() throws IOException {

qa/sql/src/main/java/org/elasticsearch/xpack/qa/sql/jdbc/ErrorsTestCase.java

@@ -12,6 +12,8 @@ import org.apache.http.entity.StringEntity;
 
 import static java.util.Collections.emptyMap;
 
+import static org.hamcrest.Matchers.startsWith;
+
 /**
  * Tests for exceptions and their messages.
  */
@@ -60,4 +62,54 @@ public class ErrorsTestCase extends JdbcIntegrationTestCase implements org.elast
             assertEquals("Found 1 problem(s)\nline 1:8: Unknown function [missing]", e.getMessage());
         }
     }
+
+    @Override
+    public void testSelectProjectScoreInAggContext() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        try (Connection c = esJdbc()) {
+            SQLException e = expectThrows(SQLException.class, () ->
+                c.prepareStatement("SELECT foo, SCORE(), COUNT(*) FROM test GROUP BY foo").executeQuery());
+            assertEquals("Found 1 problem(s)\nline 1:13: Cannot use non-grouped column [SCORE()], expected [foo]", e.getMessage());
+        }
+    }
+
+    @Override
+    public void testSelectOrderByScoreInAggContext() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        try (Connection c = esJdbc()) {
+            SQLException e = expectThrows(SQLException.class, () ->
+                c.prepareStatement("SELECT foo, COUNT(*) FROM test GROUP BY foo ORDER BY SCORE()").executeQuery());
+            assertEquals("Found 1 problem(s)\nline 1:54: Cannot order by non-grouped column [SCORE()], expected [foo]", e.getMessage());
+        }
+    }
+
+    @Override
+    public void testSelectGroupByScore() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        try (Connection c = esJdbc()) {
+            SQLException e = expectThrows(SQLException.class, () ->
+                c.prepareStatement("SELECT COUNT(*) FROM test GROUP BY SCORE()").executeQuery());
+            assertEquals("Found 1 problem(s)\nline 1:36: Cannot use [SCORE()] for grouping", e.getMessage());
+        }
+    }
+
+    @Override
+    public void testSelectScoreSubField() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        try (Connection c = esJdbc()) {
+            SQLException e = expectThrows(SQLException.class, () ->
+                c.prepareStatement("SELECT SCORE().bar FROM test").executeQuery());
+            assertThat(e.getMessage(), startsWith("line 1:15: extraneous input '.' expecting {<EOF>, ','"));
+        }
+    }
+
+    @Override
+    public void testSelectScoreInScalar() throws Exception {
+        index("test", body -> body.field("foo", 1));
+        try (Connection c = esJdbc()) {
+            SQLException e = expectThrows(SQLException.class, () ->
+                c.prepareStatement("SELECT SIN(SCORE()) FROM test").executeQuery());
+            assertThat(e.getMessage(), startsWith("Found 1 problem(s)\nline 1:12: [SCORE()] cannot be an argument to a function"));
+        }
+    }
 }

qa/sql/src/main/java/org/elasticsearch/xpack/qa/sql/jdbc/JdbcAssert.java

@@ -6,7 +6,7 @@
 package org.elasticsearch.xpack.qa.sql.jdbc;
 
 import org.apache.logging.log4j.Logger;
-
+import org.relique.jdbc.csv.CsvResultSet;
 import java.sql.JDBCType;
 import java.sql.ResultSet;
 import java.sql.ResultSetMetaData;
@@ -88,6 +88,10 @@ public class JdbcAssert {
             if (expectedType == Types.TIMESTAMP_WITH_TIMEZONE) {
                 expectedType = Types.TIMESTAMP;
             }
+            // since csv doesn't support real, we use float instead.....
+            if (expectedType == Types.FLOAT && expected instanceof CsvResultSet) {
+                expectedType = Types.REAL;
+            }
             assertEquals("Different column type for column [" + expectedName + "] (" + JDBCType.valueOf(expectedType) + " != "
                     + JDBCType.valueOf(actualType) + ")", expectedType, actualType);
         }

qa/sql/src/main/java/org/elasticsearch/xpack/qa/sql/rest/RestSqlTestCase.java

@@ -10,6 +10,7 @@ import org.apache.http.entity.ContentType;
 import org.apache.http.entity.StringEntity;
 import org.elasticsearch.client.Response;
 import org.elasticsearch.client.ResponseException;
+import org.elasticsearch.common.CheckedSupplier;
 import org.elasticsearch.common.collect.Tuple;
 import org.elasticsearch.common.io.Streams;
 import org.elasticsearch.common.xcontent.XContentHelper;
@@ -71,7 +72,11 @@ public abstract class RestSqlTestCase extends ESRestTestCase implements ErrorsTe
         client().performRequest("POST", "/test/test/_bulk", singletonMap("refresh", "true"),
                 new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
 
-        String request = "{\"query\":\"SELECT text, number, SIN(number) AS s FROM test ORDER BY number\", \"fetch_size\":2}";
+        String request = "{\"query\":\""
+                + "   SELECT text, number, SIN(number) AS s, SCORE()"
+                + "     FROM test"
+                + " ORDER BY number, SCORE()\", "
+            + "\"fetch_size\":2}";
 
         String cursor = null;
         for (int i = 0; i < 20; i += 2) {
@@ -87,11 +92,12 @@ public abstract class RestSqlTestCase extends ESRestTestCase implements ErrorsTe
                 expected.put("columns", Arrays.asList(
                         columnInfo("text", "text"),
                         columnInfo("number", "long"),
-                        columnInfo("s", "double")));
+                        columnInfo("s", "double"),
+                        columnInfo("SCORE()", "float")));
             }
             expected.put("rows", Arrays.asList(
-                    Arrays.asList("text" + i, i, Math.sin(i)),
+                    Arrays.asList("text" + i, i, Math.sin(i), 1.0),
-                    Arrays.asList("text" + (i + 1), i + 1, Math.sin(i + 1))));
+                    Arrays.asList("text" + (i + 1), i + 1, Math.sin(i + 1), 1.0)));
             expected.put("size", 2);
             cursor = (String) response.remove("cursor");
             assertResponse(expected, response);
@@ -118,6 +124,26 @@ public abstract class RestSqlTestCase extends ESRestTestCase implements ErrorsTe
                 new StringEntity("{\"query\":\"SELECT DAY_OF_YEAR(test), COUNT(*) FROM test\"}", ContentType.APPLICATION_JSON)));
     }
 
+    public void testScoreWithFieldNamedScore() throws IOException {
+        StringBuilder bulk = new StringBuilder();
+        bulk.append("{\"index\":{\"_id\":\"1\"}}\n");
+        bulk.append("{\"name\":\"test\", \"score\":10}\n");
+        client().performRequest("POST", "/test/test/_bulk", singletonMap("refresh", "true"),
+            new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
+
+        Map<String, Object> expected = new HashMap<>();
+        expected.put("columns", Arrays.asList(
+            columnInfo("name", "text"),
+            columnInfo("score", "long"),
+            columnInfo("SCORE()", "float")));
+        expected.put("rows", singletonList(Arrays.asList(
+            "test", 10, 1.0)));
+        expected.put("size", 1);
+
+        assertResponse(expected, runSql("SELECT *, SCORE() FROM test ORDER BY SCORE()"));
+        assertResponse(expected, runSql("SELECT name, \\\"score\\\", SCORE() FROM test ORDER BY SCORE()"));
+    }
+
     public void testSelectWithJoinFails() throws Exception {
         // Normal join not supported
         expectBadRequest(() -> runSql("SELECT * FROM test JOIN other"),
@@ -177,10 +203,92 @@ public abstract class RestSqlTestCase extends ESRestTestCase implements ErrorsTe
             new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
     }
 
-    private void expectBadRequest(ThrowingRunnable code, Matcher<String> errorMessageMatcher) {
+    @Override
-        ResponseException e = expectThrows(ResponseException.class, code);
+    public void testSelectProjectScoreInAggContext() throws Exception {
-        assertEquals(e.getMessage(), 400, e.getResponse().getStatusLine().getStatusCode());
+        StringBuilder bulk = new StringBuilder();
+        bulk.append("{\"index\":{\"_id\":\"1\"}}\n");
+        bulk.append("{\"foo\":1}\n");
+        client().performRequest("POST", "/test/test/_bulk", singletonMap("refresh", "true"),
+                new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
+
+        expectBadRequest(() -> runSql(
+            "     SELECT foo, SCORE(), COUNT(*)"
+            + "     FROM test"
+            + " GROUP BY foo"),
+                containsString("Cannot use non-grouped column [SCORE()], expected [foo]"));
+    }
+
+    @Override
+    public void testSelectOrderByScoreInAggContext() throws Exception {
+        StringBuilder bulk = new StringBuilder();
+        bulk.append("{\"index\":{\"_id\":\"1\"}}\n");
+        bulk.append("{\"foo\":1}\n");
+        client().performRequest("POST", "/test/test/_bulk", singletonMap("refresh", "true"),
+                new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
+
+        expectBadRequest(() -> runSql(
+            "     SELECT foo, COUNT(*)"
+            + "     FROM test"
+            + " GROUP BY foo"
+            + " ORDER BY SCORE()"),
+                containsString("Cannot order by non-grouped column [SCORE()], expected [foo]"));
+    }
+
+    @Override
+    public void testSelectGroupByScore() throws Exception {
+        StringBuilder bulk = new StringBuilder();
+        bulk.append("{\"index\":{\"_id\":\"1\"}}\n");
+        bulk.append("{\"foo\":1}\n");
+        client().performRequest("POST", "/test/test/_bulk", singletonMap("refresh", "true"),
+                new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
+
+        expectBadRequest(() -> runSql("SELECT COUNT(*) FROM test GROUP BY SCORE()"),
+                containsString("Cannot use [SCORE()] for grouping"));
+    }
+
+    @Override
+    public void testSelectScoreSubField() throws Exception {
+        StringBuilder bulk = new StringBuilder();
+        bulk.append("{\"index\":{\"_id\":\"1\"}}\n");
+        bulk.append("{\"foo\":1}\n");
+        client().performRequest("POST", "/test/test/_bulk", singletonMap("refresh", "true"),
+                new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
+
+        expectBadRequest(() -> runSql("SELECT SCORE().bar FROM test"),
+            containsString("line 1:15: extraneous input '.' expecting {<EOF>, ','"));
+    }
+
+    @Override
+    public void testSelectScoreInScalar() throws Exception {
+        StringBuilder bulk = new StringBuilder();
+        bulk.append("{\"index\":{\"_id\":\"1\"}}\n");
+        bulk.append("{\"foo\":1}\n");
+        client().performRequest("POST", "/test/test/_bulk", singletonMap("refresh", "true"),
+                new StringEntity(bulk.toString(), ContentType.APPLICATION_JSON));
+
+        expectBadRequest(() -> runSql("SELECT SIN(SCORE()) FROM test"),
+            containsString("line 1:12: [SCORE()] cannot be an argument to a function"));
+    }
+
+    private void expectBadRequest(CheckedSupplier<Map<String, Object>, Exception> code, Matcher<String> errorMessageMatcher) {
+        try {
+            Map<String, Object> result = code.get();
+            fail("expected ResponseException but got " + result);
+        } catch (ResponseException e) {
+            if (400 != e.getResponse().getStatusLine().getStatusCode()) {
+                String body;
+                try {
+                    body = Streams.copyToString(new InputStreamReader(
+                        e.getResponse().getEntity().getContent(), StandardCharsets.UTF_8));
+                } catch (IOException bre) {
+                    throw new RuntimeException("error reading body after remote sent bad status", bre);
+                }
+                fail("expected [400] response but get [" + e.getResponse().getStatusLine().getStatusCode() + "] with body:\n" +  body);
+            }
             assertThat(e.getMessage(), errorMessageMatcher);
+        } catch (Exception e) {
+            throw new AssertionError("expected ResponseException but got [" + e.getClass() + "]", e);
+        }
     }
 
     private Map<String, Object> runSql(String sql) throws IOException {
@@ -283,8 +391,7 @@ public abstract class RestSqlTestCase extends ESRestTestCase implements ErrorsTe
                 "test           \n" +
                 "test           \n";
         Tuple<String, String> response = runSqlAsText("SELECT * FROM test");
-        logger.warn(expected);
+        assertEquals(expected, response.v1());
-        logger.warn(response.v1());
     }
 
     public void testNextPageText() throws IOException {

qa/sql/src/main/resources/command.csv-spec

@@ -64,6 +64,7 @@ SIN             |SCALAR
 SINH            |SCALAR
 SQRT            |SCALAR
 TAN             |SCALAR
+SCORE           |SCORE
 ;
 
 showFunctionsWithExactMatch

qa/sql/src/main/resources/fulltext.csv-spec

@@ -29,3 +29,17 @@ SELECT emp_no, first_name, gender, last_name FROM test_emp WHERE MATCH('first_na
    emp_no:i    | first_name:s  |   gender:s    |  last_name:s
 10095          |Hilari         |M              |Morton
 ;
+
+score
+SELECT emp_no, first_name, SCORE() FROM test_emp WHERE MATCH(first_name, 'Erez') ORDER BY SCORE();
+
+   emp_no:i    | first_name:s  |   SCORE():f
+10076          |Erez           |4.2096553
+;
+
+scoreAsSomething
+SELECT emp_no, first_name, SCORE() as s FROM test_emp WHERE MATCH(first_name, 'Erez') ORDER BY SCORE();
+
+   emp_no:i    | first_name:s  |   s:f
+10076          |Erez           |4.2096553
+;

sql/server/src/main/java/org/elasticsearch/xpack/sql/analysis/analyzer/Verifier.java

@@ -6,13 +6,16 @@
 package org.elasticsearch.xpack.sql.analysis.analyzer;
 
 import org.elasticsearch.xpack.sql.capabilities.Unresolvable;
+import org.elasticsearch.xpack.sql.expression.Alias;
 import org.elasticsearch.xpack.sql.expression.Attribute;
 import org.elasticsearch.xpack.sql.expression.Expression;
 import org.elasticsearch.xpack.sql.expression.Expressions;
+import org.elasticsearch.xpack.sql.expression.Order;
 import org.elasticsearch.xpack.sql.expression.UnresolvedAttribute;
 import org.elasticsearch.xpack.sql.expression.function.Function;
 import org.elasticsearch.xpack.sql.expression.function.FunctionAttribute;
 import org.elasticsearch.xpack.sql.expression.function.Functions;
+import org.elasticsearch.xpack.sql.expression.function.Score;
 import org.elasticsearch.xpack.sql.expression.function.scalar.ScalarFunction;
 import org.elasticsearch.xpack.sql.plan.logical.Aggregate;
 import org.elasticsearch.xpack.sql.plan.logical.Filter;
@@ -150,7 +153,6 @@ abstract class Verifier {
 
         // Concrete verifications
 
-            //
         // if there are no (major) unresolved failures, do more in-depth analysis
 
         if (failures.isEmpty()) {
@@ -182,6 +184,9 @@ abstract class Verifier {
                 if (!groupingFailures.contains(p)) {
                     checkGroupBy(p, localFailures, resolvedFunctions, groupingFailures);
                 }
+
+                checkForScoreInsideFunctions(p, localFailures);
+
                 // everything checks out
                 // mark the plan as analyzed
                 if (localFailures.isEmpty()) {
@@ -256,6 +261,8 @@ abstract class Verifier {
         }
         return true;
     }
+
+
     // check whether plain columns specified in an agg are mentioned in the group-by
     private static boolean checkGroupByAgg(LogicalPlan p, Set<Failure> localFailures, Set<LogicalPlan> groupingFailures, Map<String, Function> functions) {
         if (p instanceof Aggregate) {
@@ -266,6 +273,9 @@ abstract class Verifier {
                 if (Functions.isAggregate(c)) {
                     localFailures.add(fail(c, "Cannot use an aggregate [" + c.nodeName().toUpperCase(Locale.ROOT) + "] for grouping"));
                 }
+                if (c instanceof Score) {
+                    localFailures.add(fail(c, "Cannot use [SCORE()] for grouping"));
+                }
             }));
 
             if (!localFailures.isEmpty()) {
@@ -315,15 +325,21 @@ abstract class Verifier {
         // and if that fails, start unpacking hoping to find matches
         if (e instanceof ScalarFunction) {
             ScalarFunction sf = (ScalarFunction) e;
+
             // found group for the expression
             if (Expressions.anyMatch(groupings, e::semanticEquals)) {
                 return true;
             }
+
             // unwrap function to find the base
             for (Expression arg : sf.arguments()) {
                 arg.collectFirstChildren(c -> checkGroupMatch(c, source, groupings, missing, functions));
             }
 
+            return true;
+        } else if (e instanceof Score) {
+            // Score can't be an aggretate function
+            missing.put(e, source);
             return true;
         }
 
@@ -347,4 +363,14 @@ abstract class Verifier {
         }
         return false;
     }
+
+    private static void checkForScoreInsideFunctions(LogicalPlan p, Set<Failure> localFailures) {
+        // Make sure that SCORE is only used in "top level" functions
+        p.forEachExpressions(e ->
+            e.forEachUp((Function f) ->
+                f.arguments().stream()
+                    .filter(exp -> exp.anyMatch(Score.class::isInstance))
+                    .forEach(exp -> localFailures.add(fail(exp, "[SCORE()] cannot be an argument to a function"))),
+                Function.class));
+    }
 }

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/SourceGenerator.java

@@ -26,13 +26,16 @@ import org.elasticsearch.xpack.sql.expression.NestedFieldAttribute;
 import org.elasticsearch.xpack.sql.expression.RootFieldAttribute;
 import org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition.ProcessorDefinition;
 import org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition.ReferenceInput;
+import org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition.ScoreProcessorDefinition;
 import org.elasticsearch.xpack.sql.querydsl.agg.Aggs;
 import org.elasticsearch.xpack.sql.querydsl.agg.GroupByColumnAgg;
 import org.elasticsearch.xpack.sql.querydsl.agg.GroupingAgg;
+import org.elasticsearch.xpack.sql.querydsl.container.AggRef;
 import org.elasticsearch.xpack.sql.querydsl.container.AttributeSort;
 import org.elasticsearch.xpack.sql.querydsl.container.ColumnReference;
 import org.elasticsearch.xpack.sql.querydsl.container.ComputedRef;
 import org.elasticsearch.xpack.sql.querydsl.container.QueryContainer;
+import org.elasticsearch.xpack.sql.querydsl.container.ScoreSort;
 import org.elasticsearch.xpack.sql.querydsl.container.ScriptFieldRef;
 import org.elasticsearch.xpack.sql.querydsl.container.ScriptSort;
 import org.elasticsearch.xpack.sql.querydsl.container.SearchHitFieldRef;
@@ -50,6 +53,7 @@ import java.util.Set;
 
 import static java.util.Collections.singletonList;
 import static org.elasticsearch.search.sort.SortBuilders.fieldSort;
+import static org.elasticsearch.search.sort.SortBuilders.scoreSort;
 import static org.elasticsearch.search.sort.SortBuilders.scriptSort;
 
 public abstract class SourceGenerator {
@@ -77,7 +81,7 @@ public abstract class SourceGenerator {
         Map<String, Script> scriptFields = new LinkedHashMap<>();
 
         for (ColumnReference ref : container.columns()) {
-            collectFields(ref, sourceFields, docFields, scriptFields);
+            collectFields(source, ref, sourceFields, docFields, scriptFields);
         }
 
         if (!sourceFields.isEmpty()) {
@@ -92,8 +96,6 @@ public abstract class SourceGenerator {
             source.scriptField(entry.getKey(), entry.getValue());
         }
 
-        sorting(container, source);
-
         // add the aggs
         Aggs aggs = container.aggs();
 
@@ -115,6 +117,8 @@ public abstract class SourceGenerator {
             source.aggregation(builder);
         }
 
+        sorting(container, source);
+
         // add the pipeline aggs
         for (PipelineAggregationBuilder builder : aggs.asPipelineBuilders()) {
             source.aggregation(builder);
@@ -133,25 +137,42 @@ public abstract class SourceGenerator {
         return source;
     }
 
-    private static void collectFields(ColumnReference ref, Set<String> sourceFields, Set<String> docFields, Map<String, Script> scriptFields) {
+    private static void collectFields(SearchSourceBuilder source, ColumnReference ref,
+            Set<String> sourceFields, Set<String> docFields, Map<String, Script> scriptFields) {
         if (ref instanceof ComputedRef) {
             ProcessorDefinition proc = ((ComputedRef) ref).processor();
-            proc.forEachUp(l -> collectFields(l.context(), sourceFields, docFields, scriptFields), ReferenceInput.class);
+            if (proc instanceof ScoreProcessorDefinition) {
+                /*
+                 * If we're SELECTing SCORE then force tracking scores just in case
+                 * we're not sorting on them.
+                 */
+                source.trackScores(true);
             }
-        else if (ref instanceof SearchHitFieldRef) {
+            proc.forEachUp(l -> collectFields(source, l.context(), sourceFields, docFields, scriptFields), ReferenceInput.class);
+        } else if (ref instanceof SearchHitFieldRef) {
             SearchHitFieldRef sh = (SearchHitFieldRef) ref;
             Set<String> collection = sh.useDocValue() ? docFields : sourceFields;
             collection.add(sh.name());
-        }
+        } else if (ref instanceof ScriptFieldRef) {
-        else if (ref instanceof ScriptFieldRef) {
             ScriptFieldRef sfr = (ScriptFieldRef) ref;
             scriptFields.put(sfr.name(), sfr.script().toPainless());
+        } else if (ref instanceof AggRef) {
+            // Nothing to do
+        } else {
+            throw new IllegalStateException("unhandled field in collectFields [" + ref.getClass() + "][" + ref + "]");
         }
     }
 
     private static void sorting(QueryContainer container, SearchSourceBuilder source) {
-        if (container.sort() != null) {
+        if (source.aggregations() != null && source.aggregations().count() > 0) {
-
+            // Aggs can't be sorted using search sorting. That sorting is handled elsewhere.
+            return;
+        }
+        if (container.sort() == null || container.sort().isEmpty()) {
+            // if no sorting is specified, use the _doc one
+            source.sort("_doc");
+            return;
+        }
         for (Sort sortable : container.sort()) {
             SortBuilder<?> sortBuilder = null;
 
@@ -209,10 +230,11 @@ public abstract class SourceGenerator {
 
                     sortBuilder = fieldSort;
                 }
-                }
+            } else if (sortable instanceof ScriptSort) {
-                if (sortable instanceof ScriptSort) {
                 ScriptSort ss = (ScriptSort) sortable;
                 sortBuilder = scriptSort(ss.script().toPainless(), ss.script().outputType().isNumeric() ? ScriptSortType.NUMBER : ScriptSortType.STRING);
+            } else if (sortable instanceof ScoreSort) {
+                sortBuilder = scoreSort();
             }
 
             if (sortBuilder != null) {
@@ -221,11 +243,6 @@ public abstract class SourceGenerator {
             }
         }
     }
-        else {
-            // if no sorting is specified, use the _doc one
-            source.sort("_doc");
-        }
-    }
 
     private static void optimize(QueryContainer query, SearchSourceBuilder source) {
         // if only aggs are needed, don't retrieve any docs

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/ComputingHitExtractor.java

@@ -26,6 +26,10 @@ import java.util.Objects;
  * internal implementation detail).
  */
 public class ComputingHitExtractor implements HitExtractor {
+    /**
+     * Stands for {@code comPuting}. We try to use short names for {@link HitExtractor}s
+     * to save a few bytes when when we send them back to the user.
+     */
     static final String NAME = "p";
     private final Processor processor;
 

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/ConstantExtractor.java

@@ -16,6 +16,10 @@ import java.util.Objects;
  * Returns the a constant for every search hit against which it is run.
  */
 public class ConstantExtractor implements HitExtractor {
+    /**
+     * Stands for {@code constant}. We try to use short names for {@link HitExtractor}s
+     * to save a few bytes when when we send them back to the user.
+     */
     static final String NAME = "c";
     private final Object constant;
 

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/DocValueExtractor.java

@@ -17,7 +17,11 @@ import java.io.IOException;
  * Extracts field values from {@link SearchHit#field(String)}.
  */
 public class DocValueExtractor implements HitExtractor {
-    static final String NAME = "f";
+    /**
+     * Stands for {@code doc_value}. We try to use short names for {@link HitExtractor}s
+     * to save a few bytes when when we send them back to the user.
+     */
+    static final String NAME = "d";
     private final String fieldName;
 
     public DocValueExtractor(String name) {

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/HitExtractors.java

@@ -13,7 +13,6 @@ import java.util.ArrayList;
 import java.util.List;
 
 public abstract class HitExtractors {
-
     /**
      * All of the named writeables needed to deserialize the instances of
      * {@linkplain HitExtractor}.
@@ -25,6 +24,7 @@ public abstract class HitExtractors {
         entries.add(new Entry(HitExtractor.class, InnerHitExtractor.NAME, InnerHitExtractor::new));
         entries.add(new Entry(HitExtractor.class, SourceExtractor.NAME, SourceExtractor::new));
         entries.add(new Entry(HitExtractor.class, ComputingHitExtractor.NAME, ComputingHitExtractor::new));
+        entries.add(new Entry(HitExtractor.class, ScoreExtractor.NAME, in -> ScoreExtractor.INSTANCE));
         entries.addAll(Processors.getNamedWriteables());
         return entries;
     }

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/InnerHitExtractor.java

@@ -17,6 +17,10 @@ import java.util.Map;
 import java.util.Objects;
 
 public class InnerHitExtractor implements HitExtractor {
+    /**
+     * Stands for {@code inner}. We try to use short names for {@link HitExtractor}s
+     * to save a few bytes when when we send them back to the user.
+     */
     static final String NAME = "i";
     private final String hitName, fieldName;
     private final boolean useDocValue;

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/ScoreExtractor.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.sql.execution.search.extractor;
+
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.search.SearchHit;
+
+import java.io.IOException;
+
+/**
+ * Returns the a constant for every search hit against which it is run.
+ */
+public class ScoreExtractor implements HitExtractor {
+    public static final HitExtractor INSTANCE = new ScoreExtractor();
+    /**
+     * Stands for {@code score}. We try to use short names for {@link HitExtractor}s
+     * to save a few bytes when when we send them back to the user.
+     */
+    static final String NAME = "sc";
+
+    private ScoreExtractor() {}
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        // Nothing to write
+    }
+
+    @Override
+    public String getWriteableName() {
+        return NAME;
+    }
+
+    @Override
+    public Object get(SearchHit hit) {
+        return hit.getScore();
+    }
+
+    @Override
+    public String innerHitName() {
+        return null;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == null || obj.getClass() != getClass()) {
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return 31;
+    }
+
+    @Override
+    public String toString() {
+        return "SCORE";
+    }
+}

sql/server/src/main/java/org/elasticsearch/xpack/sql/execution/search/extractor/SourceExtractor.java

@@ -13,6 +13,10 @@ import java.io.IOException;
 import java.util.Map;
 
 public class SourceExtractor implements HitExtractor {
+    /**
+     * Stands for {@code _source}. We try to use short names for {@link HitExtractor}s
+     * to save a few bytes when when we send them back to the user.
+     */
     public static final String NAME = "s";
     private final String fieldName;
 

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/Attribute.java

@@ -12,6 +12,11 @@ import java.util.Objects;
 
 import static java.util.Collections.emptyList;
 
+/**
+ * {@link Expression}s that can be converted into Elasticsearch
+ * sorts, aggregations, or queries. They can also be extracted
+ * from the result of a search.
+ */
 public abstract class Attribute extends NamedExpression {
 
     // empty - such as a top level attribute in SELECT cause

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/DefaultFunctionRegistry.java

@@ -5,6 +5,7 @@
  */
 package org.elasticsearch.xpack.sql.expression.function;
 
+import org.elasticsearch.xpack.sql.expression.function.Score;
 import org.elasticsearch.xpack.sql.expression.function.aggregate.AggregateFunction;
 import org.elasticsearch.xpack.sql.expression.function.aggregate.Avg;
 import org.elasticsearch.xpack.sql.expression.function.aggregate.Correlation;
@@ -56,18 +57,76 @@ import org.elasticsearch.xpack.sql.expression.function.scalar.math.Sin;
 import org.elasticsearch.xpack.sql.expression.function.scalar.math.Sinh;
 import org.elasticsearch.xpack.sql.expression.function.scalar.math.Sqrt;
 import org.elasticsearch.xpack.sql.expression.function.scalar.math.Tan;
-
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
 
 import static java.util.Collections.unmodifiableMap;
-import static org.elasticsearch.xpack.sql.util.CollectionUtils.combine;
+import static java.util.Collections.unmodifiableList;
 
 public class DefaultFunctionRegistry extends AbstractFunctionRegistry {
 
-    private static final Collection<Class<? extends Function>> FUNCTIONS = combine(agg(), scalar());
+    private static final Collection<Class<? extends Function>> FUNCTIONS = unmodifiableList(Arrays.asList(
+        // Aggregate functions
+            Avg.class,
+            Count.class,
+            Max.class,
+            Min.class,
+            Sum.class,
+            // Statistics
+            Mean.class,
+            StddevPop.class,
+            VarPop.class,
+            Percentile.class,
+            PercentileRank.class,
+            SumOfSquares.class,
+            // Matrix aggs
+            MatrixCount.class,
+            MatrixMean.class,
+            MatrixVariance.class,
+            Skewness.class,
+            Kurtosis.class,
+            Covariance.class,
+            Correlation.class,
+        // Scalar functions
+            // Date
+            DayOfMonth.class,
+            DayOfWeek.class,
+            DayOfYear.class,
+            HourOfDay.class,
+            MinuteOfDay.class,
+            MinuteOfHour.class,
+            SecondOfMinute.class,
+            MonthOfYear.class,
+            Year.class,
+            // Math
+            Abs.class,
+            ACos.class,
+            ASin.class,
+            ATan.class,
+            Cbrt.class,
+            Ceil.class,
+            Cos.class,
+            Cosh.class,
+            Degrees.class,
+            E.class,
+            Exp.class,
+            Expm1.class,
+            Floor.class,
+            Log.class,
+            Log10.class,
+            Pi.class,
+            Radians.class,
+            Round.class,
+            Sin.class,
+            Sinh.class,
+            Sqrt.class,
+            Tan.class,
+        // Special
+            Score.class));
 
     private static final Map<String, String> ALIASES;
     static {
@@ -92,75 +151,4 @@ public class DefaultFunctionRegistry extends AbstractFunctionRegistry {
     protected Map<String, String> aliases() {
         return ALIASES;
     }
-
-    private static Collection<Class<? extends AggregateFunction>> agg() {
-        return Arrays.asList(
-                Avg.class,
-                Count.class,
-                Max.class,
-                Min.class,
-                Sum.class,
-                // statistics
-                Mean.class,
-                StddevPop.class,
-                VarPop.class,
-                Percentile.class,
-                PercentileRank.class,
-                SumOfSquares.class,
-                // Matrix aggs
-                MatrixCount.class,
-                MatrixMean.class,
-                MatrixVariance.class,
-                Skewness.class,
-                Kurtosis.class,
-                Covariance.class,
-                Correlation.class
-                );
-    }
-    
-    private static Collection<Class<? extends ScalarFunction>> scalar() {
-        return combine(dateTimeFunctions(), 
-                mathFunctions());
-    }
-
-    private static Collection<Class<? extends ScalarFunction>> dateTimeFunctions() {
-        return Arrays.asList(
-                DayOfMonth.class,
-                DayOfWeek.class,
-                DayOfYear.class,
-                HourOfDay.class,
-                MinuteOfDay.class,
-                MinuteOfHour.class,
-                SecondOfMinute.class,
-                MonthOfYear.class,
-                Year.class
-                );
-    }
-
-    private static Collection<Class<? extends ScalarFunction>> mathFunctions() {
-        return Arrays.asList(
-                Abs.class,
-                ACos.class,
-                ASin.class,
-                ATan.class,
-                Cbrt.class,
-                Ceil.class,
-                Cos.class,
-                Cosh.class,
-                Degrees.class,
-                E.class,
-                Exp.class,
-                Expm1.class,
-                Floor.class,
-                Log.class,
-                Log10.class,
-                Pi.class,
-                Radians.class,
-                Round.class,
-                Sin.class,
-                Sinh.class,
-                Sqrt.class,
-                Tan.class
-                );
-    }
 }

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/FunctionType.java

@@ -8,11 +8,13 @@ package org.elasticsearch.xpack.sql.expression.function;
 import org.elasticsearch.xpack.sql.SqlIllegalArgumentException;
 import org.elasticsearch.xpack.sql.expression.function.aggregate.AggregateFunction;
 import org.elasticsearch.xpack.sql.expression.function.scalar.ScalarFunction;
+import org.elasticsearch.xpack.sql.expression.function.Score;
+
 
 public enum FunctionType {
-
     AGGREGATE(AggregateFunction.class),
-    SCALAR(ScalarFunction.class);
+    SCALAR(ScalarFunction.class),
+    SCORE(Score.class);
 
     private final Class<? extends Function> baseClass;
 

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/Score.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.sql.expression.function;
+
+import org.elasticsearch.xpack.sql.expression.Attribute;
+import org.elasticsearch.xpack.sql.expression.function.Function;
+import org.elasticsearch.xpack.sql.tree.Location;
+import org.elasticsearch.xpack.sql.type.DataType;
+import org.elasticsearch.xpack.sql.type.DataTypes;
+
+import static java.util.Collections.emptyList;
+
+/**
+ * Function referring to the {@code _score} in a search. Only available
+ * in the search context, and only at the "root" so it can't be combined
+ * with other function.
+ */
+public class Score extends Function {
+    public Score(Location location) {
+        super(location, emptyList());
+    }
+
+    @Override
+    public DataType dataType() {
+        return DataTypes.FLOAT;
+    }
+
+    @Override
+    public Attribute toAttribute() {
+        return new ScoreAttribute(location());
+    }
+}

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/ScoreAttribute.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.sql.expression.function;
+
+import org.elasticsearch.xpack.sql.expression.Attribute;
+import org.elasticsearch.xpack.sql.expression.ExpressionId;
+import org.elasticsearch.xpack.sql.expression.function.FunctionAttribute;
+import org.elasticsearch.xpack.sql.tree.Location;
+import org.elasticsearch.xpack.sql.type.DataType;
+import org.elasticsearch.xpack.sql.type.DataTypes;
+
+/**
+ * {@link Attribute} that represents Elasticsearch's {@code _score}.
+ */
+public class ScoreAttribute extends FunctionAttribute {
+    /**
+     * Constructor for normal use.
+     */
+    ScoreAttribute(Location location) {
+        this(location, "SCORE()", DataTypes.FLOAT, null, false, null, false);
+    }
+
+    /**
+     * Constructor for {@link #clone()}
+     */
+    private ScoreAttribute(Location location, String name, DataType dataType, String qualifier, boolean nullable, ExpressionId id,
+            boolean synthetic) {
+        super(location, name, dataType, qualifier, nullable, id, synthetic, "SCORE");
+    }
+
+    @Override
+    protected Attribute clone(Location location, String name, DataType dataType, String qualifier, boolean nullable,
+            ExpressionId id, boolean synthetic) {
+        return new ScoreAttribute(location, name, dataType, qualifier, nullable, id, synthetic);
+    }
+
+    @Override
+    protected String label() {
+        return "SCORE";
+    }
+}

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/ScalarFunction.java

@@ -38,7 +38,7 @@ public abstract class ScalarFunction extends Function {
     }
 
     @Override
-    public ScalarFunctionAttribute toAttribute() {
+    public final ScalarFunctionAttribute toAttribute() {
         if (lazyAttribute == null) {
             lazyAttribute = new ScalarFunctionAttribute(location(), name(), dataType(), id(), functionId(), asScript(), orderBy(),
                 asProcessorDefinition());

sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/processor/definition/ScoreProcessorDefinition.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition;
+
+import org.elasticsearch.xpack.sql.execution.search.extractor.ScoreExtractor;
+import org.elasticsearch.xpack.sql.expression.Expression;
+import org.elasticsearch.xpack.sql.expression.function.scalar.processor.runtime.Processor;
+import org.elasticsearch.xpack.sql.expression.function.scalar.processor.runtime.HitExtractorProcessor;
+
+import static java.util.Collections.emptyList;
+
+public class ScoreProcessorDefinition extends ProcessorDefinition {
+    public ScoreProcessorDefinition(Expression expression) {
+        super(expression, emptyList());
+    }
+
+    @Override
+    public boolean resolved() {
+        return true;
+    }
+
+    @Override
+    public Processor asProcessor() {
+        return new HitExtractorProcessor(ScoreExtractor.INSTANCE);
+    }
+}

sql/server/src/main/java/org/elasticsearch/xpack/sql/parser/ParsingException.java

@@ -45,13 +45,13 @@ public class ParsingException extends ClientSqlException {
         return super.getMessage();
     }
 
-    @Override
-    public String getMessage() {
-        return format(Locale.ROOT, "line %s:%s: %s", getLineNumber(), getColumnNumber(), getErrorMessage());
-    }
-
     @Override
     public RestStatus status() {
         return RestStatus.BAD_REQUEST;
     }
+
+    @Override
+    public String getMessage() {
+        return format(Locale.ROOT, "line %s:%s: %s", getLineNumber(), getColumnNumber(), getErrorMessage());
+    }
 }

sql/server/src/main/java/org/elasticsearch/xpack/sql/planner/PlanningException.java

@@ -12,28 +12,22 @@ import org.elasticsearch.xpack.sql.util.StringUtils;
 
 import java.util.Collection;
 import java.util.Locale;
-import java.util.Optional;
 import java.util.stream.Collectors;
 
 import static java.lang.String.format;
 
 public class PlanningException extends ClientSqlException {
-
-    private final Optional<RestStatus> status;
-
     public PlanningException(String message, Object... args) {
         super(message, args);
-        status = Optional.empty();
-    }
-
-    public PlanningException(String message, RestStatus restStatus, Object... args) {
-        super(message, args);
-        status = Optional.of(restStatus);
     }
 
     public PlanningException(Collection<Failure> sources) {
         super(extractMessage(sources));
-        status = Optional.empty();
+    }
+
+    @Override
+    public RestStatus status() {
+        return RestStatus.BAD_REQUEST;
     }
 
     private static String extractMessage(Collection<Failure> failures) {
@@ -41,9 +35,4 @@ public class PlanningException extends ClientSqlException {
                 .map(f -> format(Locale.ROOT, "line %s:%s: %s", f.source().location().getLineNumber(), f.source().location().getColumnNumber(), f.message()))
                 .collect(Collectors.joining(StringUtils.NEW_LINE, "Found " + failures.size() + " problem(s)\n", StringUtils.EMPTY));
     }
-
-    @Override
-    public RestStatus status() {
-        return status.orElse(super.status());
-    }
 }

sql/server/src/main/java/org/elasticsearch/xpack/sql/planner/QueryFolder.java

@@ -16,6 +16,7 @@ import org.elasticsearch.xpack.sql.expression.NamedExpression;
 import org.elasticsearch.xpack.sql.expression.Order;
 import org.elasticsearch.xpack.sql.expression.function.Function;
 import org.elasticsearch.xpack.sql.expression.function.Functions;
+import org.elasticsearch.xpack.sql.expression.function.ScoreAttribute;
 import org.elasticsearch.xpack.sql.expression.function.aggregate.AggregateFunction;
 import org.elasticsearch.xpack.sql.expression.function.aggregate.CompoundNumericAggregate;
 import org.elasticsearch.xpack.sql.expression.function.aggregate.Count;
@@ -46,6 +47,7 @@ import org.elasticsearch.xpack.sql.querydsl.agg.LeafAgg;
 import org.elasticsearch.xpack.sql.querydsl.container.AttributeSort;
 import org.elasticsearch.xpack.sql.querydsl.container.ComputedRef;
 import org.elasticsearch.xpack.sql.querydsl.container.QueryContainer;
+import org.elasticsearch.xpack.sql.querydsl.container.ScoreSort;
 import org.elasticsearch.xpack.sql.querydsl.container.ScriptSort;
 import org.elasticsearch.xpack.sql.querydsl.container.Sort.Direction;
 import org.elasticsearch.xpack.sql.querydsl.container.TotalCountRef;
@@ -355,13 +357,12 @@ class QueryFolder extends RuleExecutor<PhysicalPlan> {
                                 //FIXME: what about inner key
                                 queryC = withAgg.v1().addAggColumn(withAgg.v2().context());
                                 if (withAgg.v2().innerKey() != null) {
-                                    throw new PlanningException("innerkey/matrix stats not handled (yet)", RestStatus.BAD_REQUEST);
+                                    throw new PlanningException("innerkey/matrix stats not handled (yet)");
                                 }
                             }
                         }
-                    }
+                    // not an Alias or Function means it's an Attribute so apply the same logic as above
-                    // not an Alias or a Function, means it's an Attribute so apply the same logic as above
+                    } else {
-                    else {
                         GroupingAgg matchingGroup = null;
                         if (groupingContext != null) {
                             matchingGroup = groupingContext.groupFor(ne);
@@ -432,7 +433,6 @@ class QueryFolder extends RuleExecutor<PhysicalPlan> {
     private static class FoldOrderBy extends FoldingRule<OrderExec> {
         @Override
         protected PhysicalPlan rule(OrderExec plan) {
-
             if (plan.child() instanceof EsQueryExec) {
                 EsQueryExec exec = (EsQueryExec) plan.child();
                 QueryContainer qContainer = exec.queryContainer();
@@ -464,23 +464,20 @@ class QueryFolder extends RuleExecutor<PhysicalPlan> {
                             ScalarFunctionAttribute sfa = (ScalarFunctionAttribute) attr;
                             // is there an expression to order by?
                             if (sfa.orderBy() != null) {
-                                Expression ob = sfa.orderBy();
+                                if (sfa.orderBy() instanceof NamedExpression) {
-                                if (ob instanceof NamedExpression) {
+                                    Attribute at = ((NamedExpression) sfa.orderBy()).toAttribute();
-                                    Attribute at = ((NamedExpression) ob).toAttribute();
                                     at = qContainer.aliases().getOrDefault(at, at);
                                     qContainer = qContainer.sort(new AttributeSort(at, direction));
-                                }
+                                } else if (!sfa.orderBy().foldable()) {
                                     // ignore constant
-                                else if (!ob.foldable()) {
+                                    throw new PlanningException("does not know how to order by expression %s", sfa.orderBy());
-                                    throw new PlanningException("does not know how to order by expression %s", ob);
                                 }
                             }
                             // nope, use scripted sorting
-                            else {
                             qContainer = qContainer.sort(new ScriptSort(sfa.script(), direction));
-                            }
+                        } else if (attr instanceof ScoreAttribute) {
-                        }
+                            qContainer = qContainer.sort(new ScoreSort(direction));
-                        else {
+                        } else {
                             qContainer = qContainer.sort(new AttributeSort(attr, direction));
                         }
                     }

sql/server/src/main/java/org/elasticsearch/xpack/sql/querydsl/container/QueryContainer.java

@@ -15,10 +15,12 @@ import org.elasticsearch.xpack.sql.expression.Attribute;
 import org.elasticsearch.xpack.sql.expression.LiteralAttribute;
 import org.elasticsearch.xpack.sql.expression.NestedFieldAttribute;
 import org.elasticsearch.xpack.sql.expression.RootFieldAttribute;
+import org.elasticsearch.xpack.sql.expression.function.ScoreAttribute;
 import org.elasticsearch.xpack.sql.expression.function.scalar.ScalarFunctionAttribute;
 import org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition.AttributeInput;
 import org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition.ProcessorDefinition;
 import org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition.ReferenceInput;
+import org.elasticsearch.xpack.sql.expression.function.scalar.processor.definition.ScoreProcessorDefinition;
 import org.elasticsearch.xpack.sql.querydsl.agg.AggPath;
 import org.elasticsearch.xpack.sql.querydsl.agg.Aggs;
 import org.elasticsearch.xpack.sql.querydsl.agg.GroupingAgg;
@@ -287,6 +289,9 @@ public class QueryContainer {
         if (attr instanceof LiteralAttribute) {
             return new Tuple<>(this, new ComputedRef(((LiteralAttribute) attr).asProcessorDefinition()));
         }
+        if (attr instanceof ScoreAttribute) {
+            return new Tuple<>(this, new ComputedRef(new ScoreProcessorDefinition(attr)));
+        }
 
         throw new SqlIllegalArgumentException("Unknown output attribute %s", attr);
     }

sql/server/src/main/java/org/elasticsearch/xpack/sql/querydsl/container/ScoreSort.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.sql.querydsl.container;
+
+import java.util.Objects;
+
+public class ScoreSort extends Sort {
+    public ScoreSort(Direction direction) {
+        super(direction);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(direction());
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+
+        ScriptSort other = (ScriptSort) obj;
+        return Objects.equals(direction(), other.direction());
+    }
+}

sql/server/src/test/java/org/elasticsearch/xpack/sql/execution/search/SourceGeneratorTests.java

@@ -13,15 +13,26 @@ import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.search.aggregations.AggregatorFactories.Builder;
 import org.elasticsearch.search.aggregations.bucket.terms.TermsAggregationBuilder;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
+import org.elasticsearch.search.sort.SortOrder;
 import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.xpack.sql.expression.RootFieldAttribute;
+import org.elasticsearch.xpack.sql.expression.function.Score;
 import org.elasticsearch.xpack.sql.querydsl.agg.Aggs;
+import org.elasticsearch.xpack.sql.querydsl.agg.AvgAgg;
 import org.elasticsearch.xpack.sql.querydsl.agg.GroupByColumnAgg;
+import org.elasticsearch.xpack.sql.querydsl.container.AttributeSort;
 import org.elasticsearch.xpack.sql.querydsl.container.QueryContainer;
+import org.elasticsearch.xpack.sql.querydsl.container.ScoreSort;
+import org.elasticsearch.xpack.sql.querydsl.container.Sort.Direction;
 import org.elasticsearch.xpack.sql.querydsl.query.MatchQuery;
 import org.elasticsearch.xpack.sql.tree.Location;
+import org.elasticsearch.xpack.sql.type.DataTypes;
+
+import static java.util.Collections.singletonList;
+import static org.elasticsearch.search.sort.SortBuilders.fieldSort;
+import static org.elasticsearch.search.sort.SortBuilders.scoreSort;
 
 import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
 
 public class SourceGeneratorTests extends ESTestCase {
 
@@ -61,4 +72,49 @@ public class SourceGeneratorTests extends ESTestCase {
         TermsAggregationBuilder termsBuilder = (TermsAggregationBuilder) aggBuilder.getAggregatorFactories().get(0);
         assertEquals(10, termsBuilder.size());
     }
+
+    public void testSortNoneSpecified() {
+        QueryContainer container = new QueryContainer();
+        SearchSourceBuilder sourceBuilder = SourceGenerator.sourceBuilder(container, null, randomIntBetween(1, 10));
+        assertEquals(singletonList(fieldSort("_doc")), sourceBuilder.sorts());
+    }
+
+    public void testSelectScoreForcesTrackingScore() {
+        QueryContainer container = new QueryContainer()
+            .addColumn(new Score(new Location(1, 1)).toAttribute());
+        SearchSourceBuilder sourceBuilder = SourceGenerator.sourceBuilder(container, null, randomIntBetween(1, 10));
+        assertTrue(sourceBuilder.trackScores());
+    }
+
+    public void testSortScoreSpecified() {
+        QueryContainer container = new QueryContainer()
+            .sort(new ScoreSort(Direction.DESC));
+        SearchSourceBuilder sourceBuilder = SourceGenerator.sourceBuilder(container, null, randomIntBetween(1, 10));
+        assertEquals(singletonList(scoreSort()), sourceBuilder.sorts());
+    }
+
+    public void testSortFieldSpecified() {
+        QueryContainer container = new QueryContainer()
+            .sort(new AttributeSort(new RootFieldAttribute(new Location(1, 1), "test", DataTypes.KEYWORD), Direction.ASC));
+        SearchSourceBuilder sourceBuilder = SourceGenerator.sourceBuilder(container, null, randomIntBetween(1, 10));
+        assertEquals(singletonList(fieldSort("test").order(SortOrder.ASC)), sourceBuilder.sorts());
+
+        container = new QueryContainer()
+            .sort(new AttributeSort(new RootFieldAttribute(new Location(1, 1), "test", DataTypes.KEYWORD), Direction.DESC));
+        sourceBuilder = SourceGenerator.sourceBuilder(container, null, randomIntBetween(1, 10));
+        assertEquals(singletonList(fieldSort("test").order(SortOrder.DESC)), sourceBuilder.sorts());
+    }
+
+    public void testNoSort() {
+        SearchSourceBuilder sourceBuilder = SourceGenerator.sourceBuilder(new QueryContainer(), null, randomIntBetween(1, 10));
+        assertEquals(singletonList(fieldSort("_doc").order(SortOrder.ASC)), sourceBuilder.sorts());
+    }
+
+    public void testNoSortIfAgg() {
+        QueryContainer container = new QueryContainer()
+            .addGroups(singletonList(new GroupByColumnAgg("group_id", "", "group_column")))
+            .addAgg("group_id", new AvgAgg("agg_id", "", "avg_column"));
+        SearchSourceBuilder sourceBuilder = SourceGenerator.sourceBuilder(container, null, randomIntBetween(1, 10));
+        assertNull(sourceBuilder.sorts());
+    }
 }

sql/server/src/test/java/org/elasticsearch/xpack/sql/execution/search/extractor/ScoreExtractorTests.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.sql.execution.search.extractor;
+
+import org.elasticsearch.search.SearchHit;
+import org.elasticsearch.test.ESTestCase;
+
+public class ScoreExtractorTests extends ESTestCase {
+    public void testGet() {
+        int times = between(1, 1000);
+        for (int i = 0; i < times; i++) {
+            float score = randomFloat();
+            SearchHit hit = new SearchHit(1);
+            hit.score(score);
+            assertEquals(score, ScoreExtractor.INSTANCE.get(hit));
+        }
+    }
+
+    public void testToString() {
+        assertEquals("SCORE", ScoreExtractor.INSTANCE.toString());
+    }
+}

sql/server/src/test/java/org/elasticsearch/xpack/sql/parser/SqlParserTests.java

@@ -0,0 +1,130 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.sql.parser;
+
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.xpack.sql.expression.NamedExpression;
+import org.elasticsearch.xpack.sql.expression.Order;
+import org.elasticsearch.xpack.sql.expression.UnresolvedAttribute;
+import org.elasticsearch.xpack.sql.expression.UnresolvedStar;
+import org.elasticsearch.xpack.sql.expression.function.UnresolvedFunction;
+import org.elasticsearch.xpack.sql.parser.SqlParser;
+import org.elasticsearch.xpack.sql.plan.logical.LogicalPlan;
+import org.elasticsearch.xpack.sql.plan.logical.OrderBy;
+import org.elasticsearch.xpack.sql.plan.logical.Project;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.instanceOf;
+
+import static java.util.stream.Collectors.toList;
+
+public class SqlParserTests extends ESTestCase {
+    public void testSelectStar() {
+        singleProjection(project(parseStatement("SELECT * FROM foo")), UnresolvedStar.class);
+    }
+
+    private <T> T singleProjection(Project project, Class<T> type) {
+        assertThat(project.projections(), hasSize(1));
+        NamedExpression p = project.projections().get(0);
+        assertThat(p, instanceOf(type));
+        return type.cast(p);
+    }
+
+    public void testSelectField() {
+        UnresolvedAttribute a = singleProjection(project(parseStatement("SELECT bar FROM foo")), UnresolvedAttribute.class);
+        assertEquals("bar", a.name());
+    }
+
+    public void testSelectScore() {
+        UnresolvedFunction f = singleProjection(project(parseStatement("SELECT SCORE() FROM foo")), UnresolvedFunction.class);
+        assertEquals("SCORE", f.functionName());
+    }
+
+    public void testOrderByField() {
+        Order.OrderDirection dir = randomFrom(Order.OrderDirection.values());
+        OrderBy ob = orderBy(parseStatement("SELECT * FROM foo ORDER BY bar" + stringForDirection(dir)));
+        assertThat(ob.order(), hasSize(1));
+        Order o = ob.order().get(0);
+        assertEquals(dir, o.direction());
+        assertThat(o.child(), instanceOf(UnresolvedAttribute.class));
+        UnresolvedAttribute a = (UnresolvedAttribute) o.child();
+        assertEquals("bar", a.name());
+    }
+
+    public void testOrderByScore() {
+        Order.OrderDirection dir = randomFrom(Order.OrderDirection.values());
+        OrderBy ob = orderBy(parseStatement("SELECT * FROM foo ORDER BY SCORE()" + stringForDirection(dir)));
+        assertThat(ob.order(), hasSize(1));
+        Order o = ob.order().get(0);
+        assertEquals(dir, o.direction());
+        assertThat(o.child(), instanceOf(UnresolvedFunction.class));
+        UnresolvedFunction f = (UnresolvedFunction) o.child();
+        assertEquals("SCORE", f.functionName());
+    }
+
+    public void testOrderByTwo() {
+        Order.OrderDirection dir0 = randomFrom(Order.OrderDirection.values());
+        Order.OrderDirection dir1 = randomFrom(Order.OrderDirection.values());
+        OrderBy ob = orderBy(parseStatement(
+            "     SELECT *"
+            + "     FROM foo"
+            + " ORDER BY bar" + stringForDirection(dir0) + ", baz" + stringForDirection(dir1)));
+        assertThat(ob.order(), hasSize(2));
+        Order o = ob.order().get(0);
+        assertEquals(dir0, o.direction());
+        assertThat(o.child(), instanceOf(UnresolvedAttribute.class));
+        UnresolvedAttribute a = (UnresolvedAttribute) o.child();
+        assertEquals("bar", a.name());
+        o = ob.order().get(1);
+        assertEquals(dir1, o.direction());
+        assertThat(o.child(), instanceOf(UnresolvedAttribute.class));
+        a = (UnresolvedAttribute) o.child();
+        assertEquals("baz", a.name());
+    }
+
+    private LogicalPlan parseStatement(String sql) {
+        return new SqlParser().createStatement(sql);
+    }
+
+    private Project project(LogicalPlan plan) {
+        List<Project> sync = new ArrayList<Project>(1);
+        projectRecur(plan, sync);
+        assertThat("expected only one SELECT", sync, hasSize(1));
+        return sync.get(0);
+    }
+
+    private void projectRecur(LogicalPlan plan, List<Project> sync) {
+        if (plan instanceof Project) {
+            sync.add((Project) plan);
+            return;
+        }
+        for (LogicalPlan child : plan.children()) {
+            projectRecur(child, sync);
+        }
+    }
+
+    /**
+     * Find the one and only {@code ORDER BY} in a plan.
+     */
+    private OrderBy orderBy(LogicalPlan plan) {
+        List<LogicalPlan> l = plan.children().stream()
+            .filter(c -> c instanceof OrderBy)
+            .collect(toList());
+        assertThat("expected only one ORDER BY", l, hasSize(1));
+        return (OrderBy) l.get(0);
+    }
+
+    /**
+     * Convert a direction into a string that represents that parses to
+     * that direction.
+     */
+    private String stringForDirection(Order.OrderDirection dir) {
+        String dirStr = dir.toString();
+        return randomBoolean() && dirStr.equals("ASC") ? "" : " " + dirStr;
+    }
+}