gianm commented on code in PR #15634: URL: https://github.com/apache/druid/pull/15634#discussion_r1445343358
########## sql/src/main/java/org/apache/druid/sql/calcite/rule/FlattenConcatRule.java: ########## @@ -0,0 +1,125 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +package org.apache.druid.sql.calcite.rule; + +import org.apache.calcite.plan.RelOptRule; +import org.apache.calcite.plan.RelOptRuleCall; +import org.apache.calcite.plan.RelOptUtil; +import org.apache.calcite.rel.RelNode; +import org.apache.calcite.rel.rules.SubstitutionRule; +import org.apache.calcite.rex.RexBuilder; +import org.apache.calcite.rex.RexCall; +import org.apache.calcite.rex.RexNode; +import org.apache.calcite.rex.RexShuttle; +import org.apache.calcite.rex.RexUtil; +import org.apache.calcite.sql.SqlOperator; +import org.apache.calcite.sql.fun.SqlStdOperatorTable; +import org.apache.calcite.sql.type.SqlTypeFamily; +import org.apache.druid.common.config.NullHandling; +import org.apache.druid.math.expr.Function; +import org.apache.druid.sql.calcite.expression.builtin.ConcatOperatorConversion; +import org.apache.druid.sql.calcite.expression.builtin.TextcatOperatorConversion; + +import java.util.ArrayList; +import java.util.List; + +/** + * Flattens calls to CONCAT. Useful because otherwise [a || b || c] would get planned as [CONCAT(CONCAT(a, b), c)]. + */ +public class FlattenConcatRule extends RelOptRule implements SubstitutionRule +{ + public FlattenConcatRule() + { + super(operand(RelNode.class, any())); + } + + @Override + public void onMatch(RelOptRuleCall call) + { + final RelNode oldNode = call.rel(0); + final FlattenConcatShuttle shuttle = new FlattenConcatShuttle(oldNode.getCluster().getRexBuilder()); + final RelNode newNode = oldNode.accept(shuttle); + + //noinspection ObjectEquality + if (newNode != oldNode) { + call.transformTo(newNode); + call.getPlanner().prune(oldNode); + } + } + + private static class FlattenConcatShuttle extends RexShuttle + { + private final RexBuilder rexBuilder; + + public FlattenConcatShuttle(RexBuilder rexBuilder) + { + this.rexBuilder = rexBuilder; + } + + @Override + public RexNode visitCall(RexCall call) + { + if (isNonTrivialStringConcat(call)) { + final List<RexNode> newOperands = new ArrayList<>(); + for (final RexNode operand : call.getOperands()) { + if (isStringConcat(operand)) { + newOperands.addAll(((RexCall) visitCall((RexCall) operand)).getOperands()); + } else if (RexUtil.isNullLiteral(operand, true) && NullHandling.sqlCompatible()) { + return rexBuilder.makeNullLiteral(call.getType()); + } else { + newOperands.add(operand); + } + } + + if (!newOperands.equals(call.getOperands())) { + return rexBuilder.makeCall(ConcatOperatorConversion.SQL_FUNCTION, newOperands); + } else { + return call; + } + } else { + return super.visitCall(call); + } + } + } + + /** + * Whether a rex is a string concatenation operator. All of these end up being converted to + * {@link Function.ConcatFunc}. + */ + static boolean isStringConcat(final RexNode rexNode) + { + if (SqlTypeFamily.STRING.contains(rexNode.getType()) && rexNode instanceof RexCall) { + final SqlOperator operator = ((RexCall) rexNode).getOperator(); + return ConcatOperatorConversion.SQL_FUNCTION.equals(operator) + || TextcatOperatorConversion.SQL_FUNCTION.equals(operator) + || SqlStdOperatorTable.CONCAT.equals(operator); Review Comment: `SqlStdOperatorTable.CONCAT` is the standard `||` operator, i.e. `x || y || z`. `ConcatOperatorConversion.SQL_FUNCTION` is the standard `CONCAT` function, i.e. `CONCAT(x, y, z)`. `TextcatOperatorConversion.SQL_FUNCTION` is the PostgreSQL `TEXTCAT` function, provided for compatibility with PostgreSQL. It isn't documented on https://www.postgresql.org/docs/15/functions-string.html, but it is supported (try it), and it is generated by the client-side driver in certain cases. On the native Druid side, all are implemented by `concat`. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
