Github user comnetwork commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/417#discussion_r243724103
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/compile/OrderByCompiler.java ---
@@ -88,7 +88,8 @@ public static OrderBy compile(StatementContext context,
Integer offset,
RowProjector rowProjector,
TupleProjector tupleProjector,
- boolean isInRowKeyOrder) throws
SQLException {
+ boolean isInRowKeyOrder,
+ Expression whereExpression) throws
SQLException {
--- End diff --
We need the whereExpression because in
OrderPreservingTracker.IsConstantVisitor, we need whereExpression to help us to
check the columnExpression is constant or not. Just take the same sql as
example:
select a.ak3 from
(select rand() ak1,length(pk2) ak2,length(pk3) ak3,length(v1)
av1,length(v2) av2 from test order by pk2,pk3 limit 10) a
where a.ak1 = 0.0 and a.av2 = length(substr('abc',1,1))
group by a.ak3,CASE WHEN coalesce(a.ak1,1) > coalesce(a.av2,2) THEN
coalesce(a.ak1,1) ELSE coalesce(a.av2,2) END,a.av1
order by a.ak3,a.av1
We need to check if "CASE WHEN coalesce(a.ak1,1) > coalesce(a.av2,2) THEN
coalesce(a.ak1,1) ELSE coalesce(a.av2,2) END,a.av1" is constant in
OrderPreservingTracker.hasEqualityConstraints method, so we move forward to
check if the a.ak1 and a.av2 are constant in
OrderPreservingTracker.IsConstantVisitor, and we must visit the where clause
"where a.ak1 = 0.0 and a.av2 = length(substr('abc',1,1))" to check the a.ak1
and a.av2.
BTW. There is no whereExpression in current code of OrderByCompiler because
for PHOENIX-3451 which was completed by James and me before,
RowKeyColumnExpression is only supported to check in
OrderPreservingTracker.hasEqualityConstraints, and two FIXME tags were left in
this method at at time:
private boolean hasEqualityConstraints(int startPos, int endPos) {
ScanRanges ranges = context.getScanRanges();
// If a GROUP BY is being done, then the rows are ordered according
to the GROUP BY key,
// not by the original row key order of the table (see
PHOENIX-3451).
// We check each GROUP BY expression to see if it only references
columns that are
// matched by equality constraints, in which case the expression
itself would be constant.
// FIXME: this only recognizes row key columns that are held
constant, not all columns.
// FIXME: we should optimize out any GROUP BY or ORDER BY
expression which is deemed to
// be held constant based on the WHERE clause.
if (!groupBy.isEmpty()) {
In this patch, I added whereExpression to try to fix this problem to
support non-pk columns also.
---
