[GitHub] [calcite] wojustme commented on pull request #2702: [CALCITE-4800] Define a new rule of SortToSortUnifyRule in SubstitutionVisitor to support sort's match

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wojustme commented on pull request #2702:
URL: https://github.com/apache/calcite/pull/2702#issuecomment-1024816813


   Handle for Sort's mv-match
   
   - Equal collation's info, we just check offset and fetch. Query could be rewritten by mv, when mv's data-range must be larger than query's.
   such as:
   --query: 
   Sort(collation: [1], offset: 3)
     Calc(program: (expr#0..4=[{inputs}], name=[$t2], deptno=[$t1]))
       Scan(table: [hr, emps])
   --mv:
   Sort(collation: [1], offset: 2)
     Calc(program: (expr#0..4=[{inputs}], name=[$t2], deptno=[$t1]))
       Scan(table: [hr, emps])
   --rewrite:
   Sort(collation: [], offset: 1)
     Sort(collation: [1], offset: 2)
       Calc(program: (expr#0..4=[{inputs}], name=[$t2], deptno=[$t1]))
         Scan(table: [hr, emps])
   
   - No-equal collation's info, we could build a new sort above mv's, which collation must be query's
   such as:
   --query: 
   Sort(collation: [1 DESC])
     Calc(program: (expr#0..4=[{inputs}], name=[$t2], deptno=[$t1]))
       Scan(table: [hr, emps])
   --mv:
   Sort(collation: [1])
     Calc(program: (expr#0..4=[{inputs}], name=[$t2], deptno=[$t1]))
       Scan(table: [hr, emps])
   --rewrite:
   Sort(collation: [1 DESC])
     Sort(collation: [1])
       Calc(program: (expr#0..4=[{inputs}], name=[$t2], deptno=[$t1]))
         Scan(table: [hr, emps])


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