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Improve EXPLAIN to print the grouping columns in Agg and Group nodes.
Per request from Kevin Grittner.
1 parent 8693559 commit f260990

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6 files changed

+92
-30
lines changed

6 files changed

+92
-30
lines changed

‎doc/src/sgml/ref/explain.sgml‎

Lines changed: 7 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -395,13 +395,14 @@ PREPARE query(int, int) AS SELECT sum(bar) FROM test
395395

396396
EXPLAIN ANALYZE EXECUTE query(100, 200);
397397

398-
QUERY PLAN
399-
-------------------------------------------------------------------------------------------------------------------------
400-
HashAggregate (cost=39.53..39.53 rows=1 width=8) (actual time=0.661..0.672 rows=7 loops=1)
401-
-> Index Scan using test_pkey on test (cost=0.00..32.97 rows=1311 width=8) (actual time=0.050..0.395 rows=99 loops=1)
398+
QUERY PLAN
399+
------------------------------------------------------------------------------------------------------------------------
400+
HashAggregate (cost=9.54..9.54 rows=1 width=8) (actual time=0.156..0.161 rows=11 loops=1)
401+
Group Key: foo
402+
-> Index Scan using test_pkey on test (cost=0.29..9.29 rows=50 width=8) (actual time=0.039..0.091 rows=99 loops=1)
402403
Index Cond: ((id > $1) AND (id < $2))
403-
Total runtime: 0.851 ms
404-
(4 rows)
404+
Total runtime: 0.225 ms
405+
(5 rows)
405406
</programlisting>
406407
</para>
407408

‎src/backend/commands/explain.c‎

Lines changed: 65 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -76,9 +76,13 @@ static void show_sort_keys(SortState *sortstate, List *ancestors,
7676
ExplainState *es);
7777
static void show_merge_append_keys(MergeAppendState *mstate, List *ancestors,
7878
ExplainState *es);
79-
static void show_sort_keys_common(PlanState *planstate,
80-
int nkeys, AttrNumber *keycols,
81-
List *ancestors, ExplainState *es);
79+
static void show_agg_keys(AggState *astate, List *ancestors,
80+
ExplainState *es);
81+
static void show_group_keys(GroupState *gstate, List *ancestors,
82+
ExplainState *es);
83+
static void show_sort_group_keys(PlanState *planstate, const char *qlabel,
84+
int nkeys, AttrNumber *keycols,
85+
List *ancestors, ExplainState *es);
8286
static void show_sort_info(SortState *sortstate, ExplainState *es);
8387
static void show_hash_info(HashState *hashstate, ExplainState *es);
8488
static void show_instrumentation_count(const char *qlabel, int which,
@@ -1341,7 +1345,14 @@ ExplainNode(PlanState *planstate, List *ancestors,
13411345
planstate, es);
13421346
break;
13431347
case T_Agg:
1348+
show_agg_keys((AggState *) planstate, ancestors, es);
1349+
show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
1350+
if (plan->qual)
1351+
show_instrumentation_count("Rows Removed by Filter", 1,
1352+
planstate, es);
1353+
break;
13441354
case T_Group:
1355+
show_group_keys((GroupState *) planstate, ancestors, es);
13451356
show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
13461357
if (plan->qual)
13471358
show_instrumentation_count("Rows Removed by Filter", 1,
@@ -1693,9 +1704,9 @@ show_sort_keys(SortState *sortstate, List *ancestors, ExplainState *es)
16931704
{
16941705
Sort *plan = (Sort *) sortstate->ss.ps.plan;
16951706

1696-
show_sort_keys_common((PlanState *) sortstate,
1697-
plan->numCols, plan->sortColIdx,
1698-
ancestors, es);
1707+
show_sort_group_keys((PlanState *) sortstate, "Sort Key",
1708+
plan->numCols, plan->sortColIdx,
1709+
ancestors, es);
16991710
}
17001711

17011712
/*
@@ -1707,14 +1718,56 @@ show_merge_append_keys(MergeAppendState *mstate, List *ancestors,
17071718
{
17081719
MergeAppend *plan = (MergeAppend *) mstate->ps.plan;
17091720

1710-
show_sort_keys_common((PlanState *) mstate,
1711-
plan->numCols, plan->sortColIdx,
1712-
ancestors, es);
1721+
show_sort_group_keys((PlanState *) mstate, "Sort Key",
1722+
plan->numCols, plan->sortColIdx,
1723+
ancestors, es);
17131724
}
17141725

1726+
/*
1727+
* Show the grouping keys for an Agg node.
1728+
*/
1729+
static void
1730+
show_agg_keys(AggState *astate, List *ancestors,
1731+
ExplainState *es)
1732+
{
1733+
Agg *plan = (Agg *) astate->ss.ps.plan;
1734+
1735+
if (plan->numCols > 0)
1736+
{
1737+
/* The key columns refer to the tlist of the child plan */
1738+
ancestors = lcons(astate, ancestors);
1739+
show_sort_group_keys(outerPlanState(astate), "Group Key",
1740+
plan->numCols, plan->grpColIdx,
1741+
ancestors, es);
1742+
ancestors = list_delete_first(ancestors);
1743+
}
1744+
}
1745+
1746+
/*
1747+
* Show the grouping keys for a Group node.
1748+
*/
1749+
static void
1750+
show_group_keys(GroupState *gstate, List *ancestors,
1751+
ExplainState *es)
1752+
{
1753+
Group *plan = (Group *) gstate->ss.ps.plan;
1754+
1755+
/* The key columns refer to the tlist of the child plan */
1756+
ancestors = lcons(gstate, ancestors);
1757+
show_sort_group_keys(outerPlanState(gstate), "Group Key",
1758+
plan->numCols, plan->grpColIdx,
1759+
ancestors, es);
1760+
ancestors = list_delete_first(ancestors);
1761+
}
1762+
1763+
/*
1764+
* Common code to show sort/group keys, which are represented in plan nodes
1765+
* as arrays of targetlist indexes
1766+
*/
17151767
static void
1716-
show_sort_keys_common(PlanState *planstate, int nkeys, AttrNumber *keycols,
1717-
List *ancestors, ExplainState *es)
1768+
show_sort_group_keys(PlanState *planstate, const char *qlabel,
1769+
int nkeys, AttrNumber *keycols,
1770+
List *ancestors, ExplainState *es)
17181771
{
17191772
Plan *plan = planstate->plan;
17201773
List *context;
@@ -1748,7 +1801,7 @@ show_sort_keys_common(PlanState *planstate, int nkeys, AttrNumber *keycols,
17481801
result = lappend(result, exprstr);
17491802
}
17501803

1751-
ExplainPropertyList("Sort Key", result, es);
1804+
ExplainPropertyList(qlabel, result, es);
17521805
}
17531806

17541807
/*

‎src/test/regress/expected/aggregates.out‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -659,12 +659,13 @@ explain (costs off)
659659
QUERY PLAN
660660
---------------------------------------------------------------------
661661
HashAggregate
662+
Group Key: $0
662663
InitPlan 1 (returns $0)
663664
-> Limit
664665
-> Index Only Scan Backward using tenk1_unique2 on tenk1
665666
Index Cond: (unique2 IS NOT NULL)
666667
-> Result
667-
(6 rows)
668+
(7 rows)
668669

669670
select distinct max(unique2) from tenk1;
670671
max
@@ -806,6 +807,7 @@ explain (costs off)
806807
QUERY PLAN
807808
----------------------------------------------------------------------------------------------
808809
HashAggregate
810+
Group Key: $0, $1
809811
InitPlan 1 (returns $0)
810812
-> Limit
811813
-> Merge Append
@@ -831,7 +833,7 @@ explain (costs off)
831833
-> Index Only Scan Backward using minmaxtest3i on minmaxtest3 minmaxtest3_1
832834
Index Cond: (f1 IS NOT NULL)
833835
-> Result
834-
(26 rows)
836+
(27 rows)
835837

836838
select distinct min(f1), max(f1) from minmaxtest;
837839
min | max

‎src/test/regress/expected/matview.out‎

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -22,8 +22,9 @@ EXPLAIN (costs off)
2222
QUERY PLAN
2323
---------------------
2424
HashAggregate
25+
Group Key: type
2526
-> Seq Scan on t
26-
(2 rows)
27+
(3 rows)
2728

2829
CREATE MATERIALIZED VIEW tm AS SELECT type, sum(amt) AS totamt FROM t GROUP BY type WITH NO DATA;
2930
SELECT relispopulated FROM pg_class WHERE oid = 'tm'::regclass;
@@ -59,8 +60,9 @@ EXPLAIN (costs off)
5960
Sort
6061
Sort Key: t.type
6162
-> HashAggregate
63+
Group Key: t.type
6264
-> Seq Scan on t
63-
(4 rows)
65+
(5 rows)
6466

6567
CREATE MATERIALIZED VIEW tvm AS SELECT * FROM tv ORDER BY type;
6668
SELECT * FROM tvm;
@@ -82,8 +84,9 @@ EXPLAIN (costs off)
8284
---------------------------
8385
Aggregate
8486
-> HashAggregate
87+
Group Key: t.type
8588
-> Seq Scan on t
86-
(3 rows)
89+
(4 rows)
8790

8891
CREATE MATERIALIZED VIEW tvvm AS SELECT * FROM tvv;
8992
CREATE VIEW tvvmv AS SELECT * FROM tvvm;

‎src/test/regress/expected/union.out‎

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -494,12 +494,13 @@ explain (costs off)
494494
QUERY PLAN
495495
---------------------------------------------------
496496
HashAggregate
497+
Group Key: ((t1.a || t1.b))
497498
-> Append
498499
-> Index Scan using t1_ab_idx on t1
499500
Index Cond: ((a || b) = 'ab'::text)
500501
-> Index Only Scan using t2_pkey on t2
501502
Index Cond: (ab = 'ab'::text)
502-
(6 rows)
503+
(7 rows)
503504

504505
reset enable_seqscan;
505506
reset enable_indexscan;
@@ -552,17 +553,18 @@ SELECT * FROM
552553
SELECT 2 AS t, 4 AS x) ss
553554
WHERE x < 4
554555
ORDER BY x;
555-
QUERY PLAN
556-
--------------------------------
556+
QUERY PLAN
557+
--------------------------------------------------------
557558
Sort
558559
Sort Key: ss.x
559560
-> Subquery Scan on ss
560561
Filter: (ss.x < 4)
561562
-> HashAggregate
563+
Group Key: (1), (generate_series(1, 10))
562564
-> Append
563565
-> Result
564566
-> Result
565-
(8 rows)
567+
(9 rows)
566568

567569
SELECT * FROM
568570
(SELECT 1 AS t, generate_series(1,10) AS x

‎src/test/regress/expected/window.out‎

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -619,12 +619,13 @@ explain (costs off)
619619
select first_value(max(x)) over (), y
620620
from (select unique1 as x, ten+four as y from tenk1) ss
621621
group by y;
622-
QUERY PLAN
623-
-------------------------------
622+
QUERY PLAN
623+
---------------------------------------------
624624
WindowAgg
625625
-> HashAggregate
626+
Group Key: (tenk1.ten + tenk1.four)
626627
-> Seq Scan on tenk1
627-
(3 rows)
628+
(4 rows)
628629

629630
-- test non-default frame specifications
630631
SELECT four, ten,

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