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ASF GitHub Bot commented on DRILL-5879: --------------------------------------- Github user paul-rogers commented on a diff in the pull request: https://github.com/apache/drill/pull/1001#discussion_r145575103 --- Diff: exec/java-exec/src/main/codegen/templates/CastFunctionsSrcVarLenTargetVarLen.java --- @@ -73,6 +73,9 @@ public void eval() { out.start = in.start; if (charCount <= length.value || length.value == 0 ) { out.end = in.end; + if (charCount == (out.end-out.start)) { + out.asciiMode = 1; // we can conclude this string is ASCII --- End diff -- Drill likes spaces around operators: `out.end - out.start` > Optimize "Like" operator > ------------------------ > > Key: DRILL-5879 > URL: https://issues.apache.org/jira/browse/DRILL-5879 > Project: Apache Drill > Issue Type: Improvement > Components: Execution - Relational Operators > Environment: * > Reporter: salim achouche > Assignee: salim achouche > Priority: Minor > Fix For: 1.12.0 > > > Query: select <column-list> from <table> where colA like '%a%' or colA like > '%xyz%'; > Improvement Opportunities > # Avoid isAscii computation (full access of the input string) since we're > dealing with the same column twice > # Optimize the "contains" for-loop > Implementation Details > 1) > * Added a new integer variable "asciiMode" to the VarCharHolder class > * The default value is -1 which indicates this info is not known > * Otherwise this value will be set to either 1 or 0 based on the string being > in ASCII mode or Unicode > * The execution plan already shares the same VarCharHolder instance for all > evaluations of the same column value > * The asciiMode will be correctly set during the first LIKE evaluation and > will be reused across other LIKE evaluations > 2) > * The "Contains" LIKE operation is quite expensive as the code needs to > access the input string to perform character based comparisons > * Created 4 versions of the same for-loop to a) make the loop simpler to > optimize (Vectorization) and b) minimize comparisons > Benchmarks > * Lineitem table 100GB > * Query: select l_returnflag, count(*) from dfs.`<source>` where l_comment > not like '%a%' or l_comment like '%the%' group by l_returnflag > * Before changes: 33sec > * After changes : 27sec -- This message was sent by Atlassian JIRA (v6.4.14#64029)