SQL: Verify Full-Text Search functions not allowed in SELECT (#51568)

Add a verification that full-text search functions `MATCH()` and `QUERY()`
are not allowed in the SELECT clause, so that a nice error message is
returned to the user early instead of an "ugly" exception.

Fixes: #47446

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/analysis/analyzer/Verifier.java

@@ -22,6 +22,7 @@ import org.elasticsearch.xpack.ql.expression.function.Functions;
 import org.elasticsearch.xpack.ql.expression.function.aggregate.AggregateFunction;
 import org.elasticsearch.xpack.ql.expression.function.grouping.GroupingFunction;
 import org.elasticsearch.xpack.ql.expression.function.scalar.ScalarFunction;
+import org.elasticsearch.xpack.ql.expression.predicate.fulltext.FullTextPredicate;
 import org.elasticsearch.xpack.ql.plan.logical.Aggregate;
 import org.elasticsearch.xpack.ql.plan.logical.Filter;
 import org.elasticsearch.xpack.ql.plan.logical.Limit;
@@ -215,8 +216,11 @@ public final class Verifier {
         // if there are no (major) unresolved failures, do more in-depth analysis
 
         if (failures.isEmpty()) {
+            Set<Failure> localFailures = new LinkedHashSet<>();
             final Map<Attribute, Expression> collectRefs = new LinkedHashMap<>();
 
+            checkFullTextSearchInSelect(plan, localFailures);
+
             // collect Attribute sources
             // only Aliases are interesting since these are the only ones that hide expressions
             // FieldAttribute for example are self replicating.
@@ -242,8 +246,6 @@ public final class Verifier {
                     return;
                 }
 
-                Set<Failure> localFailures = new LinkedHashSet<>();
-
                 checkGroupingFunctionInGroupBy(p, localFailures);
                 checkFilterOnAggs(p, localFailures, attributeRefs);
                 checkFilterOnGrouping(p, localFailures, attributeRefs);
@@ -297,6 +299,17 @@ public final class Verifier {
         return failures;
     }
 
+    private void checkFullTextSearchInSelect(LogicalPlan plan, Set<Failure> localFailures) {
+        plan.forEachUp(p -> {
+            for (NamedExpression ne : p.projections()) {
+                ne.forEachUp((e) ->
+                        localFailures.add(fail(e, "Cannot use MATCH() or QUERY() full-text search " +
+                                "functions in the SELECT clause")),
+                        FullTextPredicate.class);
+            }
+        }, Project.class);
+    }
+
     /**
      * Check validity of Aggregate/GroupBy.
      * This rule is needed for multiple reasons:

x-pack/plugin/sql/src/test/java/org/elasticsearch/xpack/sql/analysis/analyzer/VerifierErrorMessagesTests.java

@@ -511,7 +511,7 @@ public class VerifierErrorMessagesTests extends ESTestCase {
         assertEquals("1:8: Cannot use field [x.y] with unsupported type [foobar]", error("SELECT x.y FROM test"));
     }
 
-    public void testTermEqualitOnInexact() {
+    public void testTermEqualityOnInexact() {
         assertEquals("1:26: [text = 'value'] cannot operate on first argument field of data type [text]: " +
                 "No keyword/multi-field defined exact matches for [text]; define one or use MATCH/QUERY instead",
             error("SELECT * FROM test WHERE text = 'value'"));
@@ -712,6 +712,19 @@ public class VerifierErrorMessagesTests extends ESTestCase {
             error("SELECT * FROM test WHERE text RLIKE 'foo'"));
     }
 
+    public void testMatchAndQueryFunctionsNotAllowedInSelect() {
+        assertEquals("1:8: Cannot use MATCH() or QUERY() full-text search functions in the SELECT clause",
+                error("SELECT MATCH(text, 'foo') FROM test"));
+        assertEquals("1:8: Cannot use MATCH() or QUERY() full-text search functions in the SELECT clause",
+                error("SELECT MATCH(text, 'foo') AS fullTextSearch FROM test"));
+        assertEquals("1:38: Cannot use MATCH() or QUERY() full-text search functions in the SELECT clause",
+                error("SELECT int > 10 AND (bool = false OR QUERY('foo*')) AS fullTextSearch FROM test"));
+        assertEquals("1:8: Cannot use MATCH() or QUERY() full-text search functions in the SELECT clause\n" +
+                "line 1:28: Cannot use MATCH() or QUERY() full-text search functions in the SELECT clause",
+                error("SELECT MATCH(text, 'foo'), MATCH(text, 'bar') FROM test"));
+        accept("SELECT * FROM test WHERE MATCH(text, 'foo')");
+    }
+
     public void testAllowCorrectFieldsInIncompatibleMappings() {
         assertNotNull(incompatibleAccept("SELECT languages FROM \"*\""));
     }