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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4820) Optimize OrderBy for ClientAggregatePlan
Date Thu, 27 Dec 2018 00:51:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4820?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16729234#comment-16729234
] 

ASF GitHub Bot commented on PHOENIX-4820:
-----------------------------------------

Github user twdsilva commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/417#discussion_r244065508
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/util/ExpressionUtil.java ---
    @@ -68,4 +76,144 @@ public static boolean isPkPositionChanging(TableRef tableRef, List<Expression>
p
             return false;
         }
     
    +    /**
    +     * check the whereExpression to see if the columnExpression is constant.
    +     * eg. for "where a =3 and b > 9", a is constant,but b is not.
    +     * @param columnExpression
    +     * @param whereExpression
    +     * @return
    +     */
    +    public static boolean isColumnExpressionConstant(ColumnExpression columnExpression,
Expression whereExpression) {
    +        if(whereExpression == null) {
    +            return false;
    +        }
    +        IsColumnConstantExpressionVisitor isColumnConstantExpressionVisitor =
    +                new IsColumnConstantExpressionVisitor(columnExpression);
    +        whereExpression.accept(isColumnConstantExpressionVisitor);
    +        return isColumnConstantExpressionVisitor.isConstant();
    +    }
    +
    +    private static class IsColumnConstantExpressionVisitor extends StatelessTraverseNoExpressionVisitor<Void>
{
    +        private final Expression columnExpression ;
    +        private Expression firstRhsConstantExpression = null;
    +        private int rhsConstantCount = 0;
    +        private boolean isNullExpressionVisited = false;
    +
    +        public IsColumnConstantExpressionVisitor(Expression columnExpression) {
    +            this.columnExpression = columnExpression;
    +        }
    +        /**
    +         * only conside and,for "where a = 3 or b = 9", neither a or b is constant.
    --- End diff --
    
    nit: only consider


> Optimize OrderBy for ClientAggregatePlan
> ----------------------------------------
>
>                 Key: PHOENIX-4820
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4820
>             Project: Phoenix
>          Issue Type: Improvement
>    Affects Versions: 4.14.0
>            Reporter: chenglei
>            Assignee: chenglei
>            Priority: Major
>             Fix For: 4.15.0
>
>         Attachments: PHOENIX-4820-4.x-HBase-1.3.patch, PHOENIX-4820.diff
>
>
> Given a table
> {code}
>   create table test ( 
>        pk1 varchar not null , 
>        pk2 varchar not null, 
>        pk3 varchar not null,
>         v1 varchar, 
>         v2 varchar, 
>         CONSTRAINT TEST_PK PRIMARY KEY ( 
>               pk1,
>               pk2,
>               pk3 ))
> {code}
> for following sql :
> {code}
>      select a.ak3 
>      from (select substr(pk1,1,1) ak1,substr(pk2,1,1) ak2,substr(pk3,1,1) ak3,substr(v1,1,1)
av1,substr(v2,1,1) av2 from test order by pk2,pk3 limit 10) a  group by a.ak3,a.av1 order
by a.ak3,a.av1
> {code}
> Intuitively, the above OrderBy statement {{order by a.ak3,a.av1}} should be compiled
out because it match the group by statement, but in fact it is not.
> The problem is caused by the {{QueryCompiler.compileSingleQuery}} and {{QueryCompiler.compileSingleFlatQuery}},for
 {{QueryCompiler.compileSingleQuery}} method,because the inner query has order by, so in line
520, local variable {{isInRowKeyOrder}} is false:
> {code}
> 519        context.setCurrentTable(tableRef);
> 520        boolean isInRowKeyOrder = innerPlan.getGroupBy() == GroupBy.EMPTY_GROUP_BY
&& innerPlan.getOrderBy() == OrderBy.EMPTY_ORDER_BY;
> {code}
> In {{QueryCompiler.compileSingleFlatQuery}},when {{OrderByCompiler.compile}} method is
invoked, the last parameter {{isInRowKeyOrder}} is false:
> {code}
> 562        OrderBy orderBy = OrderByCompiler.compile(context, select, groupBy, limit,
offset, projector,
> 563                groupBy == GroupBy.EMPTY_GROUP_BY ? innerPlanTupleProjector : null,
isInRowKeyOrder);
> {code}
> So in following line 156 for  {{OrderByCompiler.compile}},even though the {{tracker.isOrderPreserving}}
is true, the OrderBy  statement could not be compiled out.
> {code}
> 156       if (isInRowKeyOrder && tracker.isOrderPreserving()) {
> {code}      
> In my opinion, with GroupBy, in following line 563 for {{QueryCompiler.compileSingleFlatQuery}}
method, when we call 
> {{OrderByCompiler.compile}} method, we no need to conside the {{isInRowKeyOrder}},  just
like the previous parameter  {{tupleProjector}} does.
> {code}
>  562        OrderBy orderBy = OrderByCompiler.compile(context, select, groupBy, limit,
offset, projector,
>  563                groupBy == GroupBy.EMPTY_GROUP_BY ? innerPlanTupleProjector : null,
isInRowKeyOrder);
> {code}



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