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https://issues.apache.org/jira/browse/PHOENIX-5148?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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chenglei updated PHOENIX-5148:
------------------------------
Attachment: PHOENIX-5148-4.x-HBase-1.4.patch
> Improve OrderPreservingTracker to optimize OrderBy/GroupBy for ClientScanPlan
> and ClientAggregatePlan
> -----------------------------------------------------------------------------------------------------
>
> Key: PHOENIX-5148
> URL: https://issues.apache.org/jira/browse/PHOENIX-5148
> Project: Phoenix
> Issue Type: Improvement
> Affects Versions: 4.14.1
> Reporter: chenglei
> Assignee: chenglei
> Priority: Major
> Fix For: 4.15.0
>
> Attachments: PHOENIX-5148-4.x-HBase-1.4.patch
>
>
> Given a table
> {code:java}
> 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}
> Consider following three cases:
> *1. OrderBy of ClientScanPlan*
> for sql:
> {code:java}
> select v1 from (select v1,v2,pk3 from test t where pk1 = '6' order by
> t.v2,t.pk3,t.v1 limit 10) a order by v2,pk3
> {code}
> Obviously, the outer {{OrderBy}} "order by v2,pk3" should be compiled out
> because it matchs the inner query {{OrderBy}} "order by t.v2,t.pk3,t.v1" ,
> but unfortunately it is not compiled out.
> *2. GroupBy of ClientAggregatePlan*
> for sql :
> {code:java}
> select v1 from (select v1,pk2,pk1 from test t where pk1 = '6' order by
> t.pk2,t.v1,t.pk1 limit 10) a group by pk2,v1
> {code}
> Obviously, the outer {{GroupBy}} "group by pk2,v1" should be orderPreserving
> because it matchs the inner query {{OrderBy}} "order by t.pk2,t.v1,t.pk1" ,
> but unfortunately the {{isOrderPreserving()}} of outer {{GroupBy}} return
> false.
> *3. OrderBy of SortMergeJoinPlan(from PHOENIX-4618)*
> for sql:
> {code:java}
> SELECT * FROM T1 JOIN T2 ON T1.a = T2.a and T1.b = T2.b{code}
> The result of the sort-merge-join is sorted on (T1.a, T1.b) and (T2.a, T2.b)
> at the same time.
> Thus, both 1)
> {code:java}
> SELECT * FROM T1 JOIN T2 ON T1.a = T2.a and T1.b = T2.b ORDER BY T1.a,
> T1.b{code}
> and 2)
> {code:java}
> SELECT * FROM T1 JOIN T2 ON T1.a = T2.a and T1.b = T2.b ORDER BY T2.a,
> T2.b{code}
> should avoid doing an extra order-by after the sort-merge-join operation.
>
> All the above three cases are caused by the same problem that the
> {{OrderPreservingTracker}} relies solely on row keys for inferring alignment
> between the target {{Expression}} and the source sortedness.
> For following {{QueryCompiler.compileSingleQuery}}, because the inner query
> of above cases has {{OrderBy}}, so in line 534, local variable
> {{isInRowKeyOrder}} is false:
> {code:java}
> 518 protected QueryPlan compileSingleQuery(StatementContext context,
> SelectStatement select, List<Object> binds, boolean asSubquery, boolean
> allowPageFilter) throws SQLException{
> 519 SelectStatement innerSelect = select.getInnerSelectStatement();
> 520 if (innerSelect == null) {
> 521 return compileSingleFlatQuery(context, select, binds,
> asSubquery, allowPageFilter, null, null, true);
> 522 }
> 523
> 524 QueryPlan innerPlan = compileSubquery(innerSelect, false);
> 525 TupleProjector tupleProjector = new
> TupleProjector(innerPlan.getProjector());
> 526 innerPlan = new TupleProjectionPlan(innerPlan, tupleProjector,
> null);
> 527
> 528 // Replace the original resolver and table with those having
> compiled type info.
> 529 TableRef tableRef = context.getResolver().getTables().get(0);
> 530 ColumnResolver resolver =
> FromCompiler.getResolverForCompiledDerivedTable(statement.getConnection(),
> tableRef, innerPlan.getProjector());
> 531 context.setResolver(resolver);
> 532 tableRef = resolver.getTables().get(0);
> 533 context.setCurrentTable(tableRef);
> 534 boolean isInRowKeyOrder = innerPlan.getGroupBy() ==
> GroupBy.EMPTY_GROUP_BY && innerPlan.getOrderBy() == OrderBy.EMPTY_ORDER_BY;
> 535
> 536 return compileSingleFlatQuery(context, select, binds,
> asSubquery, allowPageFilter, innerPlan, tupleProjector, isInRowKeyOrder);
> 537 }
> {code}
> Because the {{OrderPreservingTracker}} relies solely on row keys, so in
> following line 170 of {{OrderByCompiler.compile}} , when {{isInRowKeyOrder}}
> is false, the {{OrderPreservingTracker.isOrderPreserving()}} checking is
> skipped:
> {code:java}
> 169 // If we're ordering by the order returned by the scan, we don't need
> an order by
> 170 if (isInRowKeyOrder && tracker.isOrderPreserving()) {
> 171 if (tracker.isReverse()) {
> 172 // Don't use reverse scan if:
> 173 // 1) we're using a skip scan, as our skip scan doesn't
> support this yet.
> 174 // 2) we have the FORWARD_SCAN hint set to choose to
> keep loading of column
> 175 // families on demand versus doing a reverse scan
> 176 // REV_ROW_KEY_ORDER_BY scan would not take effect for a
> projected table, so don't return it for such table types.
> 177 if
> (context.getConnection().getQueryServices().getProps().getBoolean(QueryServices.USE_REVERSE_SCAN_ATTRIB,
> QueryServicesOptions.DEFAULT_USE_REVERSE_SCAN)
> 178 && !context.getScanRanges().useSkipScanFilter()
> 179 && context.getCurrentTable().getTable().getType()
> != PTableType.PROJECTED
> 180 && context.getCurrentTable().getTable().getType()
> != PTableType.SUBQUERY
> 181 &&
> !statement.getHint().hasHint(Hint.FORWARD_SCAN)) {
> 182 return OrderBy.REV_ROW_KEY_ORDER_BY;
> 183 }
> 184 } else {
> 185 return OrderBy.FWD_ROW_KEY_ORDER_BY;
> 186 }
> 187 }
> {code}
>
> What we can do to fix this problem are :
> - refactor the {{OrderPreservingTracker}} to make it inferring alignment
> between the target {{Expression}} and the source sortedness based on
> {{OrderByExpression}} , not the row keys, so we can remove the variable
> {{isInRowKeyOrder}}.
> - add a new method {{getActualOutputOrderBys}} to the {{QueryPlan}} to get
> the output OrderBys of the query result , eg. for the above third
> {{SortMergeJoinPlan}} example ,{{getActualOutputOrderBys}} returns (T1.a,
> T1.b) and (T2.a, T2.b) .
> Besides above three cases, a implicit semantic optimization could be
> implemented also:
> for following sql , even the literal {{OrderBy}} of inner query is "order by
> t.pk1,t.pk2" . By {{getActualOutputOrderBys}} of inner {{QueryPlan}}, we can
> infer that the actual {{OrderBy}} of inner query is "order by
> t.pk1,t.pk2,t.pk3" , so the outer OrderBy "order by pk1,pk2,pk3" could be
> compiled out:
> {code}
> select pk1 from (select pk3,pk2,pk1 from test t where v1 = '6' order by
> t.pk1,t.pk2 limit 10) a where pk3 > '8' order by pk1,pk2,pk3
> {code}
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