yaooqinn opened a new pull request #26640: [SPARK-30000][SQL] Trim the string when cast string type to decimals URL: https://github.com/apache/spark/pull/26640 ### What changes were proposed in this pull request? https://bugs.openjdk.java.net/browse/JDK-8170259 https://bugs.openjdk.java.net/browse/JDK-8170563 When we cast string type to decimal type, we rely on java.math. BigDecimal. It can't accept leading and training spaces, as you can see in the above links. This behavior is not consistent with other numeric types now. we need to fix it and keep consistency. ### Why are the changes needed? make string to numeric types be consistent ### Does this PR introduce any user-facing change? yes, string removed trailing or leading white spaces will be able to convert to decimal if the trimmed is valid ### How was this patch tested? <!-- If tests were added, say they were added here. Please make sure to add some test cases that check the changes thoroughly including negative and positive cases if possible. If it was tested in a way different from regular unit tests, please clarify how you tested step by step, ideally copy and paste-able, so that other reviewers can test and check, and descendants can verify in the future. If tests were not added, please describe why they were not added and/or why it was difficult to add. --> 1. modify ut #### Benchmark ```scala /* * 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.spark.sql.execution.benchmark import org.apache.spark.benchmark.Benchmark /** * Benchmark trim the string when casting string type to Boolean/Numeric types. * To run this benchmark: * {{{ * 1. without sbt: * bin/spark-submit --class <this class> --jars <spark core test jar> <spark sql test jar> * 2. build/sbt "sql/test:runMain <this class>" * 3. generate result: SPARK_GENERATE_BENCHMARK_FILES=1 build/sbt "sql/test:runMain <this class>" * Results will be written to "benchmarks/CastBenchmark-results.txt". * }}} */ object CastBenchmark extends SqlBasedBenchmark { override def runBenchmarkSuite(mainArgs: Array[String]): Unit = { val title = "Cast String to Integral" runBenchmark(title) { withTempPath { dir => val N = 500L << 14 val df = spark.range(N) val types = Seq("decimal") (1 to 5).by(2).foreach { i => df.selectExpr(s"concat(id, '${" " * i}') as str") .write.mode("overwrite").parquet(dir + i.toString) } val benchmark = new Benchmark(title, N, minNumIters = 5, output = output) Seq(true, false).foreach { trim => types.foreach { t => val str = if (trim) "trim(str)" else "str" val expr = s"cast($str as $t) as c_$t" (1 to 5).by(2).foreach { i => benchmark.addCase(expr + s" - with $i spaces") { _ => spark.read.parquet(dir + i.toString).selectExpr(expr).collect() } } } } benchmark.run() } } } } ``` #### string trim vs not trim ```java [info] Java HotSpot(TM) 64-Bit Server VM 1.8.0_231-b11 on Mac OS X 10.15.1 [info] Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz [info] Cast String to Integral: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative [info] ------------------------------------------------------------------------------------------------------------------------ [info] cast(trim(str) as decimal) as c_decimal - with 1 spaces 3362 5486 NaN 2.4 410.4 1.0X [info] cast(trim(str) as decimal) as c_decimal - with 3 spaces 3251 5655 NaN 2.5 396.8 1.0X [info] cast(trim(str) as decimal) as c_decimal - with 5 spaces 3208 5725 NaN 2.6 391.7 1.0X [info] cast(str as decimal) as c_decimal - with 1 spaces 13962 16233 1354 0.6 1704.3 0.2X [info] cast(str as decimal) as c_decimal - with 3 spaces 14273 14444 179 0.6 1742.4 0.2X [info] cast(str as decimal) as c_decimal - with 5 spaces 14318 14535 125 0.6 1747.8 0.2X ``` #### string trim vs this fix ```java [info] Java HotSpot(TM) 64-Bit Server VM 1.8.0_231-b11 on Mac OS X 10.15.1 [info] Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz [info] Cast String to Integral: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative [info] ------------------------------------------------------------------------------------------------------------------------ [info] cast(trim(str) as decimal) as c_decimal - with 1 spaces 3265 6299 NaN 2.5 398.6 1.0X [info] cast(trim(str) as decimal) as c_decimal - with 3 spaces 3183 6241 693 2.6 388.5 1.0X [info] cast(trim(str) as decimal) as c_decimal - with 5 spaces 3167 5923 1151 2.6 386.7 1.0X [info] cast(str as decimal) as c_decimal - with 1 spaces 3161 5838 1126 2.6 385.9 1.0X [info] cast(str as decimal) as c_decimal - with 3 spaces 3046 3457 837 2.7 371.8 1.1X [info] cast(str as decimal) as c_decimal - with 5 spaces 3053 4445 NaN 2.7 372.7 1.1X [info] ```
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