amrishlal commented on a change in pull request #7394: URL: https://github.com/apache/pinot/pull/7394#discussion_r706855461
########## File path: pinot-core/src/main/java/org/apache/pinot/core/query/optimizer/statement/StringPredicateFilterOptimizer.java ########## @@ -0,0 +1,119 @@ +/** + * 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.pinot.core.query.optimizer.statement; + +import java.util.List; +import javax.annotation.Nullable; +import org.apache.pinot.common.request.Expression; +import org.apache.pinot.common.request.ExpressionType; +import org.apache.pinot.common.request.Function; +import org.apache.pinot.common.request.PinotQuery; +import org.apache.pinot.pql.parsers.pql2.ast.FilterKind; +import org.apache.pinot.spi.config.table.TableConfig; +import org.apache.pinot.spi.data.FieldSpec; +import org.apache.pinot.spi.data.Schema; + + +/** + * Given two column names 'strColumn1' and 'strColumn1', CalciteSqlParser.queryRewrite will turn WHERE and HAVING + * expressions of form "strColumn1 <operator> strColumn2" into "MINUS(strColumn1,strColumn2) <operator> 0" regardless + * of the column datatype. The resulting query will fail to evaluate since the MINUS operator does not work with the + * STRING column type. This class rewrites expressions of form "MINUS(strColumn1,strColumn2) <operator> 0" to + * "STRCMP(strColumn1, strColumn2) <operator> 0" to fix the issue. + * + * Currently, rewrite phase (see CalciteSqlParser.queryRewrite) does not have access to schema; hence, we need to again + * rewrite MINUS(strColumn1, strColumn2) into STRCMP(strColumn1, strColumn2). At some point, we should merge query + * rewrite phase with optimizer phase to avoid such issues altogether. + */ +public class StringPredicateFilterOptimizer implements StatementOptimizer { + private static final String MINUS_OPERATOR_NAME = "MINUS"; + private static final String STRCMP_OPERATOR_NAME = "STRCMP"; + + @Override + public void optimize(PinotQuery query, @Nullable TableConfig tableConfig, @Nullable Schema schema) { + if (schema == null) { + return; + } + + Expression filter = query.getFilterExpression(); + if (filter != null) { + optimizeExpression(filter, schema); + } + + Expression expression = query.getHavingExpression(); + if (expression != null) { + optimizeExpression(expression, schema); + } + } + + /** Traverse an expression tree to replace MINUS function with STRCMP if function operands are STRING. */ + private static void optimizeExpression(Expression expression, Schema schema) { + ExpressionType type = expression.getType(); + if (type != ExpressionType.FUNCTION) { + // We have nothing to rewrite if expression is not a function. + return; + } + + Function function = expression.getFunctionCall(); + String operator = function.getOperator(); + List<Expression> operands = function.getOperands(); + FilterKind kind = FilterKind.valueOf(operator); + switch (kind) { + case AND: + case OR: { + for (Expression operand : operands) { + optimizeExpression(operand, schema); + } + break; + } + default: { + replaceMinusWithCompareForStrings(operands.get(0), schema); + break; + } + } + } + + /** Replace the operator of a MINUS function with COMPARE if both operands are STRING. */ + private static void replaceMinusWithCompareForStrings(Expression expression, Schema schema) { + if (expression.getType() != ExpressionType.FUNCTION) { + // We have nothing to rewrite if expression is not a function. + return; + } + + Function function = expression.getFunctionCall(); + String operator = function.getOperator(); + List<Expression> operands = function.getOperands(); + if (operator.equals(MINUS_OPERATOR_NAME) && operands.size() == 2 && isStringColumn(operands.get(0), schema) + && isStringColumn(operands.get(1), schema)) { + function.setOperator(STRCMP_OPERATOR_NAME); + } + } + + /** @return true if expression is a column of string type. */ + private static boolean isStringColumn(Expression expression, Schema schema) { + if (expression.getType() != ExpressionType.IDENTIFIER) { + // Expression is not a column. + return false; + } + + String column = expression.getIdentifier().getName(); + FieldSpec fieldSpec = schema.getFieldSpecFor(column); + return fieldSpec == null ? false : fieldSpec.getDataType() == FieldSpec.DataType.STRING; Review comment: Fixed. -- This is an automated message from the Apache Git Service. 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