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Improve LIKE pushdown for ClickHouse complex expression
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plugin/trino-clickhouse/src/main/java/io/trino/plugin/clickhouse/expression/RewriteLike.java
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| /* | ||
| * Licensed 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 io.trino.plugin.clickhouse.expression; | ||
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| import com.google.common.collect.ImmutableList; | ||
| import io.airlift.slice.Slice; | ||
| import io.trino.matching.Capture; | ||
| import io.trino.matching.Captures; | ||
| import io.trino.matching.Pattern; | ||
| import io.trino.plugin.base.expression.ConnectorExpressionRule; | ||
| import io.trino.plugin.jdbc.QueryParameter; | ||
| import io.trino.plugin.jdbc.expression.ParameterizedExpression; | ||
| import io.trino.spi.expression.Call; | ||
| import io.trino.spi.expression.Constant; | ||
| import io.trino.spi.expression.Variable; | ||
| import io.trino.spi.type.CharType; | ||
| import io.trino.spi.type.VarcharType; | ||
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| import java.util.Optional; | ||
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| import static com.google.common.base.Preconditions.checkArgument; | ||
| import static io.trino.matching.Capture.newCapture; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.argument; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.argumentCount; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.call; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.constant; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.functionName; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.type; | ||
| import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.variable; | ||
| import static io.trino.plugin.clickhouse.ClickHouseClient.supportsPushdown; | ||
| import static io.trino.spi.expression.StandardFunctions.LIKE_FUNCTION_NAME; | ||
| import static io.trino.spi.type.BooleanType.BOOLEAN; | ||
| import static java.lang.String.format; | ||
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| public class RewriteLike | ||
| implements ConnectorExpressionRule<Call, ParameterizedExpression> | ||
| { | ||
| private static final Capture<Variable> LIKE_VALUE = newCapture(); | ||
| // TODO allow Variable as a LIKE_PATTERN: "SELECT * FROM t WHERE column_a LIKE column_b" is a valid query in ClickHouse | ||
| // only Constant is allowed as LIKE_PATTERN, because according to | ||
| // https://clickhouse.com/docs/en/sql-reference/functions/string-search-functions#like | ||
| // ClickHouse requires backslashes in strings to be quoted as well, so you would actually need to write \\%, \\_ and \\\\ to match against literal %, _ and \ | ||
| // if "column_a LIKE column_b" is pushed down, it requires more thorough consideration how to process escaping. | ||
| private static final Capture<Constant> LIKE_PATTERN = newCapture(); | ||
| private static final Pattern<Call> PATTERN = call() | ||
| .with(functionName().equalTo(LIKE_FUNCTION_NAME)) | ||
| .with(type().equalTo(BOOLEAN)) | ||
| .with(argumentCount().equalTo(2)) | ||
| .with(argument(0).matching(variable() | ||
| .with(type().matching(type -> type instanceof CharType || type instanceof VarcharType)) | ||
| .matching((Variable variable, RewriteContext<ParameterizedExpression> context) -> supportsPushdown(variable, context)) | ||
| .capturedAs(LIKE_VALUE))) | ||
| .with(argument(1).matching(constant() | ||
| .with(type().matching(type -> type instanceof CharType || type instanceof VarcharType)) | ||
| .capturedAs(LIKE_PATTERN))); | ||
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| @Override | ||
| public Pattern<Call> getPattern() | ||
| { | ||
| return PATTERN; | ||
| } | ||
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| @Override | ||
| public Optional<ParameterizedExpression> rewrite(Call expression, Captures captures, RewriteContext<ParameterizedExpression> context) | ||
| { | ||
| Variable likeValue = captures.get(LIKE_VALUE); | ||
| Constant likePattern = captures.get(LIKE_PATTERN); | ||
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| checkArgument(likePattern.getValue() != null, "When pattern is NULL, optimizer shortcuts to return fast, not reaching connector expression"); | ||
| if (((Slice) likePattern.getValue()).toStringUtf8().contains("\\")) { | ||
| // LIKE in trino does not support escape characters. | ||
| // However Clickhouse supports them with \ is for escaping literals %, _ and \. | ||
| // ClickHouse requires backslashes in strings to be quoted as well, so you would actually need to write \\%, \\_ and \\\\ to match against literal %, _ and \ | ||
| // So just to translate Trino LIKE '\' , all \ have to be escaped, and resulting clickhouse should be LIKE '\\\\' | ||
| // TODO escape `\` appropriately and pushdown: .replace("\\", "\\\\\\\\") | ||
| return Optional.empty(); | ||
| } | ||
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| return context.defaultRewrite(likeValue).flatMap(value -> | ||
| context.defaultRewrite(likePattern).map(pattern -> | ||
| new ParameterizedExpression( | ||
| format("%s LIKE %s", value.expression(), pattern.expression()), | ||
| ImmutableList.<QueryParameter>builder() | ||
| .addAll(value.parameters()) | ||
| .addAll(pattern.parameters()) | ||
| .build()))); | ||
| } | ||
| } |
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