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https://issues.apache.org/jira/browse/CALCITE-2630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16657907#comment-16657907
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Julian Hyde commented on CALCITE-2630:
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The other principle I am drawing on - which has served us well - is minimalism.
The standard says that IN is expanded to OR. Therefore OR is syntactic sugar.
If people write the same query using equivalent IN or OR formulations we should
generate the same plan. With your scheme we would not.
> 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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