SQL: Fix incorrect field type returned by SYS TYPE (elastic/x-pack-elasticsearch#4358)

SYS TYPE returns an integer instead of a boolean (the bug was caused
by reading the ODBC spec which refers to the wire representation instead
of the JDBC one which uses primitives)

Original commit: elastic/x-pack-elasticsearch@f9fe64ab0d

plugin/sql/src/main/java/org/elasticsearch/xpack/sql/plan/logical/command/sys/SysTypes.java

@@ -83,7 +83,7 @@ public class SysTypes extends Command {
                         // only numerics are signed
                         !t.isSigned(),
                         //no fixed precision scale SQL_FALSE
-                        0,
+                        false,
                         null,
                         null,
                         null,

plugin/sql/src/test/java/org/elasticsearch/xpack/sql/plan/logical/command/sys/SysParserTests.java

@@ -66,6 +66,8 @@ public class SysParserTests extends ESTestCase {
             assertFalse(r.schema().types().contains(DataType.NULL));
             // test numeric as signed
             assertFalse(r.column(9, Boolean.class));
+            // make sure precision is returned as boolean (not int)
+            assertFalse(r.column(10, Boolean.class));
             
             for (int i = 0; i < r.size(); i++) {
                 assertEquals(names.get(i), r.column(0));