[CALCITE-6819] MSSQL doesn't support TRUE/FALSE keywords in its Join …

…predicate

In MSSQL dialect use 1=1 instead of TRUE

core/src/main/java/org/apache/calcite/adapter/jdbc/JdbcRules.java

@@ -51,7 +51,7 @@
 import org.apache.calcite.rel.core.Values;
 import org.apache.calcite.rel.metadata.RelMdUtil;
 import org.apache.calcite.rel.metadata.RelMetadataQuery;
-import org.apache.calcite.rel.rel2sql.SqlImplementor;
+import org.apache.calcite.rel.rel2sql.RelToSqlConverter;
 import org.apache.calcite.rel.type.RelDataType;
 import org.apache.calcite.rex.RexCall;
 import org.apache.calcite.rex.RexLiteral;
@@ -329,7 +329,7 @@ protected JdbcJoinRule(Config config) {
      * Returns whether a condition is supported by {@link JdbcJoin}.
      *
      * <p>Corresponds to the capabilities of
-     * {@link SqlImplementor#convertConditionToSqlNode}.
+     * {@link RelToSqlConverter#convertConditionToSqlNode}.
      *
      * @param node Condition
      * @return Whether condition is supported

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

@@ -221,6 +221,26 @@ private static class AliasReplacementShuttle extends SqlShuttle {
     }
   }
 
+  /**
+   * Converts a {@link RexNode} condition into a {@link SqlNode}.
+   *
+   * @param node            Join condition
+   * @param leftContext     Left context
+   * @param rightContext    Right context
+   *
+   * @return SqlNode that represents the condition
+   */
+  public SqlNode convertConditionToSqlNode(RexNode node,
+      Context leftContext,
+      Context rightContext) {
+    if (node.isAlwaysTrue() || node.isAlwaysFalse()) {
+      return dialect.emulateJoinConditionTrueFalse(node);
+    }
+    final Context joinContext =
+        leftContext.implementor().joinContext(leftContext, rightContext);
+    return joinContext.toSql(null, node);
+  }
+
   /** Visits a Join; called by {@link #dispatch} via reflection. */
   public Result visit(Join e) {
     switch (e.getJoinType()) {

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

@@ -316,29 +316,6 @@ public Result setOpToSql(SqlSetOperator operator, RelNode rel) {
     return result(node, clauses, rel, null);
   }
 
-  /**
-   * Converts a {@link RexNode} condition into a {@link SqlNode}.
-   *
-   * @param node            Join condition
-   * @param leftContext     Left context
-   * @param rightContext    Right context
-   *
-   * @return SqlNode that represents the condition
-   */
-  public static SqlNode convertConditionToSqlNode(RexNode node,
-      Context leftContext,
-      Context rightContext) {
-    if (node.isAlwaysTrue()) {
-      return SqlLiteral.createBoolean(true, POS);
-    }
-    if (node.isAlwaysFalse()) {
-      return SqlLiteral.createBoolean(false, POS);
-    }
-    final Context joinContext =
-        leftContext.implementor().joinContext(leftContext, rightContext);
-    return joinContext.toSql(null, node);
-  }
-
   /** Removes cast from string.
    *
    * <p>For example, {@code x > CAST('2015-01-07' AS DATE)}

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

@@ -943,6 +943,18 @@ public JoinType emulateJoinTypeForCrossJoin() {
     return JoinType.COMMA;
   }
 
+  /**
+   * Writes TRUE/FALSE or 1 = 1/ 1 <> 1 for certain
+   * database variants (MSSQL, currently).
+   */
+  public SqlNode emulateJoinConditionTrueFalse(RexNode node) {
+    if (node.isAlwaysTrue()) {
+      return SqlLiteral.createBoolean(true, SqlParserPos.ZERO);
+    } else {
+      return SqlLiteral.createBoolean(false, SqlParserPos.ZERO);
+    }
+  }
+
   protected @Nullable SqlNode emulateNullDirectionWithIsNull(SqlNode node,
       boolean nullsFirst, boolean desc) {
     // No need for emulation if the nulls will anyways come out the way we want

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

@@ -21,6 +21,7 @@
 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.rex.RexNode;
 import org.apache.calcite.sql.SqlAbstractDateTimeLiteral;
 import org.apache.calcite.sql.SqlBasicFunction;
 import org.apache.calcite.sql.SqlCall;
@@ -33,6 +34,7 @@
 import org.apache.calcite.sql.SqlLiteral;
 import org.apache.calcite.sql.SqlNode;
 import org.apache.calcite.sql.SqlNodeList;
+import org.apache.calcite.sql.SqlNumericLiteral;
 import org.apache.calcite.sql.SqlOperator;
 import org.apache.calcite.sql.SqlSyntax;
 import org.apache.calcite.sql.SqlUtil;
@@ -43,6 +45,8 @@
 import org.apache.calcite.sql.type.ReturnTypes;
 import org.apache.calcite.sql.type.SqlTypeName;
 
+import com.google.common.collect.ImmutableList;
+
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 import static java.util.Objects.requireNonNull;
@@ -128,6 +132,18 @@ public MssqlSqlDialect(Context context) {
     }
   }
 
+  @Override public SqlNode emulateJoinConditionTrueFalse(RexNode node) {
+    final SqlParserPos pos = SqlParserPos.ZERO;
+    SqlNumericLiteral oneLiteral = SqlLiteral.createExactNumeric("1", pos);
+    if (node.isAlwaysTrue()) {
+      return SqlStdOperatorTable.EQUALS.createCall(pos,
+          ImmutableList.of(oneLiteral, oneLiteral));
+    } else {
+      return SqlStdOperatorTable.NOT_EQUALS.createCall(pos,
+          ImmutableList.of(oneLiteral, oneLiteral));
+    }
+  }
+
   @Override public void unparseOffsetFetch(SqlWriter writer, @Nullable SqlNode offset,
       @Nullable SqlNode fetch) {
     if (!top && offset != null) {

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

@@ -9093,7 +9093,35 @@ private void checkLiteral2(String expression, String expected) {
         .dialect(MssqlSqlDialect.DEFAULT).ok(mssqlExpected);
   }
 
- /** Test case for
+  @Test void testMSSQLJoinAlwaysTrue() {
+    final String query = "SELECT \"hire_date\", \"department_description\" FROM \"employee\" "
+        + "LEFT JOIN \"department\" ON TRUE";
+    final String mssqlExpected = "SELECT [employee].[hire_date],"
+        + " [department].[department_description]\nFROM [foodmart].[employee]\nLEFT JOIN"
+        + " [foodmart].[department] ON 1 = 1";
+    final String mysqlExpected = "SELECT `employee`.`hire_date`,"
+        + " `department`.`department_description`\nFROM `foodmart`.`employee`\nLEFT JOIN"
+        + " `foodmart`.`department` ON TRUE";
+    sql(query)
+        .dialect(MssqlSqlDialect.DEFAULT).ok(mssqlExpected)
+        .dialect(MysqlSqlDialect.DEFAULT).ok(mysqlExpected);
+  }
+
+  @Test void testMSSQLJoinAlwaysFalse() {
+    final String query = "SELECT \"hire_date\", \"department_description\" FROM \"employee\" "
+        + "LEFT JOIN \"department\" ON False";
+    final String mssqlExpected = "SELECT [employee].[hire_date],"
+        + " [department].[department_description]\nFROM [foodmart].[employee]\nLEFT JOIN"
+        + " [foodmart].[department] ON 1 <> 1";
+    final String mysqlExpected = "SELECT `employee`.`hire_date`,"
+        + " `department`.`department_description`\nFROM `foodmart`.`employee`\nLEFT JOIN"
+        + " `foodmart`.`department` ON FALSE";
+    sql(query)
+        .dialect(MssqlSqlDialect.DEFAULT).ok(mssqlExpected)
+        .dialect(MysqlSqlDialect.DEFAULT).ok(mysqlExpected);
+  }
+
+  /** Test case for
    * <a href="https://issues.apache.org/jira/browse/CALCITE-6726">[CALCITE-6726]
    * Add translation for MOD operator in MSSQL</a>.
    */