[CALCITE-6220] Rewrite MIN/MAX(bool) as BOOL_AND/BOOL_OR for Postgres…

…, Redshift

core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java

@@ -81,6 +81,7 @@
 import org.apache.calcite.sql.SqlUpdate;
 import org.apache.calcite.sql.SqlUtil;
 import org.apache.calcite.sql.fun.SqlInternalOperators;
+import org.apache.calcite.sql.fun.SqlMinMaxAggFunction;
 import org.apache.calcite.sql.fun.SqlSingleValueAggFunction;
 import org.apache.calcite.sql.fun.SqlStdOperatorTable;
 import org.apache.calcite.sql.parser.SqlParserPos;
@@ -577,6 +578,8 @@ protected Builder buildAggregate(Aggregate e, Builder builder,
       RelDataType aggCallRelDataType = aggCall.getType();
       if (aggCall.getAggregation() instanceof SqlSingleValueAggFunction) {
         aggCallSqlNode = dialect.rewriteSingleValueExpr(aggCallSqlNode, aggCallRelDataType);
+      } else if (aggCall.getAggregation() instanceof SqlMinMaxAggFunction) {
+        aggCallSqlNode = dialect.rewriteMaxMinExpr(aggCallSqlNode, aggCallRelDataType);
       }
       addSelect(selectList, aggCallSqlNode, e.getRowType());
     }

core/src/main/java/org/apache/calcite/sql/SqlDialect.java

@@ -872,6 +872,13 @@ public SqlNode rewriteSingleValueExpr(SqlNode aggCall, RelDataType relDataType)
     return aggCall;
   }
 
+  /** With x as BOOLEAN column, rewrite MAX(x)/MIN(x) as BOOL_OR(x)/BOOL_AND(x)
+   * for certain database variants (Postgres and Redshift, currently).
+   */
+  public SqlNode rewriteMaxMinExpr(SqlNode aggCall, RelDataType relDataType) {
+    return aggCall;
+  }
+
   /**
    * Returns the SqlNode for emulating the null direction for the given field
    * or <code>null</code> if no emulation needs to be done.

core/src/main/java/org/apache/calcite/sql/dialect/PostgresqlSqlDialect.java

@@ -173,12 +173,16 @@ public PostgresqlSqlDialect(Context context) {
               timeUnitNode.getParserPosition());
       SqlFloorFunction.unparseDatetimeFunction(writer, call2, "DATE_TRUNC", false);
       break;
-
     default:
       super.unparseCall(writer, call, leftPrec, rightPrec);
     }
   }
 
+  @Override public SqlNode rewriteMaxMinExpr(SqlNode aggCall, RelDataType relDataType) {
+    RedshiftSqlDialect redshiftSqlDialect = new RedshiftSqlDialect(DEFAULT_CONTEXT);
+    return redshiftSqlDialect.rewriteMaxMinExpr(aggCall, relDataType);
+  }
+
   @Override public boolean supportsGroupByLiteral() {
     return false;
   }

core/src/main/java/org/apache/calcite/sql/dialect/RedshiftSqlDialect.java

@@ -20,11 +20,15 @@
 import org.apache.calcite.rel.type.RelDataType;
 import org.apache.calcite.rel.type.RelDataTypeSystem;
 import org.apache.calcite.rel.type.RelDataTypeSystemImpl;
+import org.apache.calcite.sql.SqlBasicCall;
 import org.apache.calcite.sql.SqlDataTypeSpec;
 import org.apache.calcite.sql.SqlDialect;
+import org.apache.calcite.sql.SqlKind;
 import org.apache.calcite.sql.SqlNode;
+import org.apache.calcite.sql.SqlOperator;
 import org.apache.calcite.sql.SqlUserDefinedTypeNameSpec;
 import org.apache.calcite.sql.SqlWriter;
+import org.apache.calcite.sql.fun.SqlLibraryOperators;
 import org.apache.calcite.sql.parser.SqlParserPos;
 import org.apache.calcite.sql.type.SqlTypeName;
 
@@ -107,6 +111,21 @@ public RedshiftSqlDialect(Context context) {
         SqlParserPos.ZERO);
   }
 
+  @Override public SqlNode rewriteMaxMinExpr(SqlNode aggCall, RelDataType relDataType) {
+    // The behavior of this method depends on the argument type,
+    // and whether it is MIN/MAX
+    final SqlTypeName type = relDataType.getSqlTypeName();
+    final boolean isMax = aggCall.getKind() == SqlKind.MAX;
+    // If the type is BOOLEAN, create a new call to the correct operator
+    if (type == SqlTypeName.BOOLEAN) {
+      final SqlOperator op = isMax ? SqlLibraryOperators.BOOL_OR : SqlLibraryOperators.BOOL_AND;
+      final SqlNode operand = ((SqlBasicCall) aggCall).operand(0);
+      return op.createCall(SqlParserPos.ZERO, operand);
+    }
+    // Otherwise, just return as it arrived
+    return aggCall;
+  }
+
   @Override public boolean supportsGroupByLiteral() {
     return false;
   }

core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java

@@ -6677,12 +6677,37 @@ private void checkLiteral2(String expression, String expected) {
    * Add BITAND_AGG, BITOR_AGG functions (enabled in Snowflake library)</a>. */
   @Test void testBitOrAgg() {
     final String query = "select bit_or(\"product_id\")\n"
-        + "from \"product\"";
+      	+ "from \"product\"";
     final String expectedSnowflake = "SELECT BITOR_AGG(\"product_id\")\n"
-        + "FROM \"foodmart\".\"product\"";
+      	+ "FROM \"foodmart\".\"product\"";
     sql(query).withLibrary(SqlLibrary.SNOWFLAKE).withSnowflake().ok(expectedSnowflake);
   }
 
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-6220">[CALCITE-6220]
+   * Rewrite MIN/MAX(bool) as BOOL_AND/BOOL_OR for Postgres, Redshift</a>. */
+  @Test void testMaxMinOnBooleanColumn() {
+    final String query = "select max(\"brand_name\" = 'a'), "
+        + "min(\"brand_name\" = 'a'), "
+        + "min(\"brand_name\")\n"
+        + "from \"product\"";
+    final String expected = "SELECT MAX(\"brand_name\" = 'a'), "
+        + "MIN(\"brand_name\" = 'a'), "
+        + "MIN(\"brand_name\")\n"
+        + "FROM \"foodmart\".\"product\"";
+    final String expectedPostgres = "SELECT BOOL_OR(\"brand_name\" = 'a'), "
+        + "BOOL_AND(\"brand_name\" = 'a'), "
+        + "MIN(\"brand_name\")\n"
+        + "FROM \"foodmart\".\"product\"";
+    final String expectedRedshift = "SELECT BOOL_OR(\"brand_name\" = 'a'), "
+        + "BOOL_AND(\"brand_name\" = 'a'), "
+        + "MIN(\"brand_name\")\n"
+        + "FROM \"foodmart\".\"product\"";
+    sql(query).ok(expected);
+    sql(query).withPostgresql().ok(expectedPostgres);
+    sql(query).withRedshift().ok(expectedRedshift);
+  }
+
   /** Test case for
    * <a href="https://issues.apache.org/jira/browse/CALCITE-6156">[CALCITE-6156]
    * Add ENDSWITH, STARTSWITH functions (enabled in Postgres, Snowflake libraries)</a>. */