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https://issues.apache.org/jira/browse/CALCITE-5473?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17676612#comment-17676612
]
Thomas Rebele commented on CALCITE-5473:
----------------------------------------
Potentially this could avoid the sort in the following example query (in
combination with CALCITE-5472):
{noformat}
0: jdbc:calcite:example/csv/src/test/resource> explain plan for select a,b+10
from (values (1,2,3), (2, 3, 4), (3,10,10) ) T(a,b,c) ORDER BY a,b+10;
+--------------------------------------------------------------------------------------------------+
| PLAN
|
+--------------------------------------------------------------------------------------------------+
| EnumerableSort(sort0=[$0], sort1=[$1], dir0=[ASC], dir1=[ASC])
EnumerableCalc(expr#0..2=[{inputs}], expr#3=[10], expr#4=[+($t1, $t3)],
A=[$t0], EXPR$1=[$t4])
EnumerableValues(tuples=[[{ 1, 2, 3 }, { 2, 3, 4 }, { 3, 10, 10 }]])
|
+--------------------------------------------------------------------------------------------------+
1 row selected (0.015 seconds)
0: jdbc:calcite:example/csv/src/test/resource> explain plan for select a,b+10
from (values (1,2,3), (2, 3, 4), (3,10,10) ) T(a,b,c) ORDER BY a,b;
+---------------------------------------------------------------------------------------------------------+
| PLAN
|
+---------------------------------------------------------------------------------------------------------+
| EnumerableCalc(expr#0..2=[{inputs}], expr#3=[10], expr#4=[+($t1, $t3)],
A=[$t0], EXPR$1=[$t4], B=[$t1])
EnumerableValues(tuples=[[{ 1, 2, 3 }, { 2, 3, 4 }, { 3, 10, 10 }]])
|
+---------------------------------------------------------------------------------------------------------+
1 row selected (0.017 seconds) {noformat}
> Keep more collations in RelMdCollation#project for monotonic RexCalls
> ---------------------------------------------------------------------
>
> Key: CALCITE-5473
> URL: https://issues.apache.org/jira/browse/CALCITE-5473
> Project: Calcite
> Issue Type: Improvement
> Reporter: Thomas Rebele
> Priority: Major
>
> Some RexCalls do not affect the collation, i.e., $0+10 has the same collation
> as $0 (if there are now integer overflows). This is already implemented in
> {{{}SqlMonotonicBinaryOperator#getMonotonicity{}}}.
> If we have an input with collation [0,1], and a {{{}Calc(a=$0+10, b=$1){}}},
> then the output collation would be [0, 1] as well. This is the case for
> STRICTLY_INCREASING or STRICTLY_DECREASING calls (though the direction of the
> field collation might need to be adapted).
> However, if the Calc was {{{}Calc(a=FLOOR($0), b=$1){}}}, then the output
> collation would be just [0], as the sortedness of b is not guaranteed. This
> happens for example with rows (0.2, 50) and (0.3, 20) and (0.4, 30), in that
> order. So for INCREASING, DECREASING, or CONSTANT the collation would be
> shortened.
> The right place to implement this would probably be
> {{{}RelMdCollation#project{}}}. The {{fieldCollationsForRexCalls}} loop would
> need to stay, because some calls may introduce a collation, regardless of the
> input. E.g., {{SELECT CURRENT_DATE FROM some_random_table}} is always sorted.
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