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From "Paul Rogers (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-5200) Nested query fails to push filter down near scan
Date Mon, 16 Jan 2017 19:52:26 GMT
Paul Rogers created DRILL-5200:
----------------------------------

             Summary: Nested query fails to push filter down near scan
                 Key: DRILL-5200
                 URL: https://issues.apache.org/jira/browse/DRILL-5200
             Project: Apache Drill
          Issue Type: Bug
    Affects Versions: 1.9.0
            Reporter: Paul Rogers
            Priority: Minor


Consider the query described in DRILL-5198. The query was deliberately designed to do a full
sort and discard results. Unfortunately, the query succeeded when it should not have been
able to do so. The query:

{code}
select * from (select * from dfs.`/big-csv-file.csv` order by columns[0])d where d.columns[0]
= 'bogus value';
{code}

The resulting plan. Note that the filter (which removes all rows) is above the sort; should
be below.

{code}
00-00    Screen : rowType = RecordType(ANY *): rowcount = 2.691360795E7, cumulative cost =
{1.6444214457450001E9 rows, 2.6992589029593388E10 cpu, 0.0 io, 3.67460460544E12 network, 2.870784848E9
memory}, id = 459
00-01      Project(*=[$0]) : rowType = RecordType(ANY *): rowcount = 2.691360795E7, cumulative
cost = {1.64173008495E9 rows, 2.698989766879839E10 cpu, 0.0 io, 3.67460460544E12 network,
2.870784848E9 memory}, id = 458
00-02        SelectionVectorRemover : rowType = RecordType(ANY T0¦¦*): rowcount = 2.691360795E7,
cumulative cost = {1.64173008495E9 rows, 2.698989766879839E10 cpu, 0.0 io, 3.67460460544E12
network, 2.870784848E9 memory}, id = 457
00-03          Filter(condition=[=(ITEM(ITEM($0, 'columns'), 0), 'ljdfhwuehnoiueyf')]) : rowType
= RecordType(ANY T0¦¦*): rowcount = 2.691360795E7, cumulative cost = {1.614816477E9 rows,
2.696298406084839E10 cpu, 0.0 io, 3.67460460544E12 network, 2.870784848E9 memory}, id = 456
00-04            Project(T0¦¦*=[$0]) : rowType = RecordType(ANY T0¦¦*): rowcount = 1.79424053E8,
cumulative cost = {1.435392424E9 rows, 2.613763341704839E10 cpu, 0.0 io, 3.67460460544E12
network, 2.870784848E9 memory}, id = 455
00-05              SingleMergeExchange(sort0=[1 ASC]) : rowType = RecordType(ANY T0¦¦*,
ANY EXPR$1): rowcount = 1.79424053E8, cumulative cost = {1.435392424E9 rows, 2.613763341704839E10
cpu, 0.0 io, 3.67460460544E12 network, 2.870784848E9 memory}, id = 454
01-01                SelectionVectorRemover : rowType = RecordType(ANY T0¦¦*, ANY EXPR$1):
rowcount = 1.79424053E8, cumulative cost = {1.255968371E9 rows, 2.470224099304839E10 cpu,
0.0 io, 2.204762763264E12 network, 2.870784848E9 memory}, id = 453
01-02                  Sort(sort0=[$1], dir0=[ASC]) : rowType = RecordType(ANY T0¦¦*, ANY
EXPR$1): rowcount = 1.79424053E8, cumulative cost = {1.076544318E9 rows, 2.452281694004839E10
cpu, 0.0 io, 2.204762763264E12 network, 2.870784848E9 memory}, id = 452
01-03                    Project(T0¦¦*=[$0], EXPR$1=[$1]) : rowType = RecordType(ANY T0¦¦*,
ANY EXPR$1): rowcount = 1.79424053E8, cumulative cost = {8.97120265E8 rows, 4.844449431E9
cpu, 0.0 io, 2.204762763264E12 network, 0.0 memory}, id = 451
01-04                      HashToRandomExchange(dist0=[[$1]]) : rowType = RecordType(ANY T0¦¦*,
ANY EXPR$1, ANY E_X_P_R_H_A_S_H_F_I_E_L_D): rowcount = 1.79424053E8, cumulative cost = {8.97120265E8
rows, 4.844449431E9 cpu, 0.0 io, 2.204762763264E12 network, 0.0 memory}, id = 450
02-01                        UnorderedMuxExchange : rowType = RecordType(ANY T0¦¦*, ANY
EXPR$1, ANY E_X_P_R_H_A_S_H_F_I_E_L_D): rowcount = 1.79424053E8, cumulative cost = {7.17696212E8
rows, 1.973664583E9 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 449
03-01                          Project(T0¦¦*=[$0], EXPR$1=[$1], E_X_P_R_H_A_S_H_F_I_E_L_D=[hash32AsDouble($1)])
: rowType = RecordType(ANY T0¦¦*, ANY EXPR$1, ANY E_X_P_R_H_A_S_H_F_I_E_L_D): rowcount =
1.79424053E8, cumulative cost = {5.38272159E8 rows, 1.79424053E9 cpu, 0.0 io, 0.0 network,
0.0 memory}, id = 448
03-02                            Project(T0¦¦*=[$0], EXPR$1=[ITEM($1, 0)]) : rowType = RecordType(ANY
T0¦¦*, ANY EXPR$1): rowcount = 1.79424053E8, cumulative cost = {3.58848106E8 rows, 1.076544318E9
cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 447
03-03                              Project(T0¦¦*=[$0], columns=[$1]) : rowType = RecordType(ANY
T0¦¦*, ANY columns): rowcount = 1.79424053E8, cumulative cost = {1.79424053E8 rows, 3.58848106E8
cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 446
03-04                                Scan(groupscan=[EasyGroupScan [selectionRoot=maprfs:/drill/testdata/resource-manager/descending-col-length-8k.tbl,
numFiles=1, columns=[`*`], files=[maprfs:///drill/testdata/resource-manager/descending-col-length-8k.tbl]]])
: rowType = (DrillRecordRow[*, columns]): rowcount = 1.79424053E8, cumulative cost = {1.79424053E8
rows, 3.58848106E8 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 445
{code}

What should have happened is that the filter was pushed down near the scan. It is likely that
the clever nested query structure used used in the query tricks the planner into missing an
optimization opportunity.



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