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[Kernel][Expressions] Add support for LIKE expression (#3103)
## Description Add SQL `LIKE` expression support in Kernel list of supported expressions and a default implementation. Addresses part of #2539 (where `STARTS_WITH` as `LIKE 'str%'`) ## How was this patch tested? added unit tests Signed-off-by: Krishnan Paranji Ravi <krishna.pr@gmail.com>
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.../src/main/java/io/delta/kernel/defaults/internal/expressions/LikeExpressionEvaluator.java
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| /* | ||
| * Copyright (2023) The Delta Lake Project Authors. | ||
| * | ||
| * 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.delta.kernel.defaults.internal.expressions; | ||
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| import java.util.ArrayList; | ||
| import java.util.Arrays; | ||
| import java.util.List; | ||
| import java.util.Objects; | ||
| import java.util.regex.Pattern; | ||
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| import io.delta.kernel.data.ColumnVector; | ||
| import io.delta.kernel.expressions.Expression; | ||
| import io.delta.kernel.expressions.Literal; | ||
| import io.delta.kernel.expressions.Predicate; | ||
| import io.delta.kernel.types.BooleanType; | ||
| import io.delta.kernel.types.DataType; | ||
| import io.delta.kernel.types.StringType; | ||
| import io.delta.kernel.internal.util.Utils; | ||
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| import static io.delta.kernel.defaults.internal.DefaultEngineErrors.invalidEscapeSequence; | ||
| import static io.delta.kernel.defaults.internal.DefaultEngineErrors.unsupportedExpressionException; | ||
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| /** | ||
| * Utility methods to evaluate {@code like} expression. | ||
| */ | ||
| public class LikeExpressionEvaluator { | ||
| private LikeExpressionEvaluator() { | ||
| } | ||
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| static Predicate validateAndTransform( | ||
| Predicate like, | ||
| List<Expression> childrenExpressions, | ||
| List<DataType> childrenOutputTypes) { | ||
| int size = childrenExpressions.size(); | ||
| if (size < 2 || size > 3) { | ||
| throw unsupportedExpressionException(like, | ||
| "Invalid number of inputs to LIKE expression. " + | ||
| "Example usage: LIKE(column, 'test%'), LIKE(column, 'test\\[%', '\\')"); | ||
| } | ||
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| Expression left = childrenExpressions.get(0); | ||
| DataType leftOutputType = childrenOutputTypes.get(0); | ||
| Expression right = childrenExpressions.get(1); | ||
| DataType rightOutputType = childrenOutputTypes.get(1); | ||
| Expression escapeCharExpr = size == 3 ? childrenExpressions.get(2) : null; | ||
| DataType escapeCharOutputType = size == 3 ? childrenOutputTypes.get(2) : null; | ||
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| if (!(StringType.STRING.equivalent(leftOutputType) | ||
| && StringType.STRING.equivalent(rightOutputType))) { | ||
| throw unsupportedExpressionException(like, | ||
| "LIKE is only supported for string type expressions"); | ||
| } | ||
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| if (escapeCharExpr != null && | ||
| (!(escapeCharExpr instanceof Literal && | ||
| StringType.STRING.equivalent(escapeCharOutputType)))) { | ||
| throw unsupportedExpressionException(like, | ||
| "LIKE expects escape token expression to be a literal of String type"); | ||
| } | ||
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| Literal literal = (Literal) escapeCharExpr; | ||
| if (literal != null && | ||
| literal.getValue().toString().length() != 1) { | ||
| throw unsupportedExpressionException(like, | ||
| "LIKE expects escape token to be a single character"); | ||
| } | ||
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| List<Expression> children = new ArrayList<>(Arrays.asList(left, right)); | ||
| if(Objects.nonNull(escapeCharExpr)) { | ||
| children.add(escapeCharExpr); | ||
| } | ||
| return new Predicate(like.getName(), children); | ||
| } | ||
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| static ColumnVector eval(List<ColumnVector> children) { | ||
| final char DEFAULT_ESCAPE_CHAR = '\\'; | ||
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| return new ColumnVector() { | ||
| final ColumnVector escapeCharVector = | ||
| children.size() == 3 ? | ||
| children.get(2) : | ||
| null; | ||
| final ColumnVector left = children.get(0); | ||
| final ColumnVector right = children.get(1); | ||
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| Character escapeChar = null; | ||
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| public void initEscapeCharIfRequired() { | ||
| if (escapeChar == null) { | ||
| escapeChar = | ||
| escapeCharVector != null && !escapeCharVector.getString(0).isEmpty() ? | ||
| escapeCharVector.getString(0).charAt(0) : | ||
| DEFAULT_ESCAPE_CHAR; | ||
| } | ||
| } | ||
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| @Override | ||
| public DataType getDataType() { | ||
| return BooleanType.BOOLEAN; | ||
| } | ||
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| @Override | ||
| public int getSize() { | ||
| return left.getSize(); | ||
| } | ||
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| @Override | ||
| public void close() { | ||
| Utils.closeCloseables(left, right); | ||
| } | ||
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| @Override | ||
| public boolean getBoolean(int rowId) { | ||
| initEscapeCharIfRequired(); | ||
| return isLike(left.getString(rowId), right.getString(rowId), escapeChar); | ||
| } | ||
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| @Override | ||
| public boolean isNullAt(int rowId) { | ||
| return left.isNullAt(rowId) || right.isNullAt(rowId); | ||
| } | ||
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| public boolean isLike(String input, String pattern, char escape) { | ||
| if (!Objects.isNull(input) && !Objects.isNull(pattern)) { | ||
| String regex = escapeLikeRegex(pattern, escape); | ||
| return input.matches(regex); | ||
| } | ||
| return false; | ||
| } | ||
| }; | ||
| } | ||
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| /** | ||
| * utility method to convert a predicate pattern to a java regex | ||
| * @param pattern the pattern used in the expression | ||
| * @param escape escape character to use | ||
| * @return java regex | ||
| */ | ||
| private static String escapeLikeRegex(String pattern, char escape) { | ||
| final int len = pattern.length(); | ||
| final StringBuilder javaPattern = new StringBuilder(len + len); | ||
| for (int i = 0; i < len; i++) { | ||
| char c = pattern.charAt(i); | ||
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| if (c == escape) { | ||
| if (i == (pattern.length() - 1)) { | ||
| throw invalidEscapeSequence(pattern, i); | ||
| } | ||
| char nextChar = pattern.charAt(i + 1); | ||
| if ((nextChar == '_') | ||
| || (nextChar == '%') | ||
| || (nextChar == escape)) { | ||
| javaPattern.append(Pattern.quote(Character.toString(nextChar))); | ||
| i++; | ||
| } else { | ||
| throw invalidEscapeSequence(pattern, i); | ||
| } | ||
| } else if (c == '_') { | ||
| javaPattern.append('.'); | ||
| } else if (c == '%') { | ||
| javaPattern.append(".*"); | ||
| } else { | ||
| javaPattern.append(Pattern.quote(Character.toString(c))); | ||
| } | ||
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| } | ||
| return "(?s)" + javaPattern; | ||
| } | ||
| } |
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