[jira] [Commented] (CALCITE-2630) Convert SqlInOperator to In-Expression

["Juhwan Kim (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-2630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16918163#comment-16918163 ] 

Juhwan Kim commented on CALCITE-2630:
-------------------------------------

I also agree with the idea of leaving IN as is. Of course, we could let IN exist only in SqlNode land, convert OR to IN before code generation, and let the runtime engine do the hash lookup. However, this gets trickier if we have NOT IN. After firing ReduceExpressionsRule, NOT with OR conditions would probably end up becoming AND with not equal conditions. We could explicitly handle this case and generate IN from there, but, having IN as it is seems to be a better option.

> Convert SqlInOperator to In-Expression
> --------------------------------------
>
>                 Key: CALCITE-2630
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2630
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.17.0
>            Reporter: pengzhiwei
>            Assignee: pengzhiwei
>            Priority: Major
>
> Currently Calcite translate "IN" to "OR" expression when the count of  IN's operands less than "inSubQueryThreshold" or  to "Join" when the operands count greater  than "inSubQueryThreshold" to get better performance.
>   However this translation to "JOIN" is so complex. Especially when the "IN" expression located in the "select" or "join on condition".
> For example:
> {code:java}
> select case when deptno in (1,2) then 0 else 1 end from emp
> {code}
> the logical plan generated as follow:
> {code:java}
> LogicalProject(EXPR$0=[CASE(CAST(CASE(=($9, 0), false, IS NOT NULL($13), true, IS NULL($11), null, <($10, $9), null, false)):BOOLEAN NOT NULL, 0, 1)])
> LogicalJoin(condition=[=($11, $12)], joinType=[left])
>  LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8], $f0=[$9], $f1=[$10], DEPTNO0=[$7])
>   LogicalJoin(condition=[true], joinType=[inner])
>     LogicalTableScan(table=[[CATALOG, SALES, EMP]])
>     LogicalAggregate(group=[{}], agg#0=[COUNT()], agg#1=[COUNT($0)])
>      LogicalProject(ROW_VALUE=[$0], $f1=[true])
>       LogicalValues(tuples=[[{ 1 }, { 2 }]])
>   LogicalAggregate(group=[{0}], agg#0=[MIN($1)])
>     LogicalProject(ROW_VALUE=[$0], $f1=[true])
>       LogicalValues(tuples=[[{ 1 }, { 2 }]])
> {code}
> The generated logical plan is so complex for such a simple sql！
> I think we can treat "IN" as a function like "plus" and "minus".So there is no translation on "IN" and just keep it as it is.This would be much clear in the logical plan!
> In the execute stage,We can provide a "InExpression":
> {code:java}
> InExpression(left,condition0,condition1,...) {code}
>  We can put all the constant conditions to a "Set".In that way,the computational complexity can reduce from O（n）to O(1).
> It would be much clear and have a good performance. 
> PS: "In sub-query" is not included in our talk.



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