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Commit4526951

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Make postgres_fdw's "Relations" output agree with the rest of EXPLAIN.
The relation aliases shown in the "Relations" line for a foreign scandidn't always agree with those used in the rest of EXPLAIN's output.The regression test result changes appearing here provide examples.It's really impossible for postgres_fdw to duplicate EXPLAIN's aliasassignment logic during postgresGetForeignRelSize(), because of thede-duplication that EXPLAIN does on a global basis --- and anyway,trying to duplicate that would be unmaintainable. Instead, just putnumeric rangetable indexes into the string, and convert those totable names/aliases in postgresExplainForeignScan, which does haveaccess to the results of ruleutils.c's alias assignment logic.Aside from being more reliable, this shifts some work from planningto EXPLAIN, which is a good tradeoff for performance. (I alsochanged from using StringInfo to using psprintf, which makes thecode slightly simpler and reduces its memory consumption.)A kluge required by this solution is that we have to reverse-engineerthe rtoffset applied by setrefs.c. If that logic ever fails(presumably because the member tables of a join got offset bydifferent amounts), we'll need some more cooperation with setrefs.cto keep things straight. But for now, there's no need for that.Arguably this is a back-patchable bug fix, but since this is a mostlycosmetic issue and there have been no field complaints, I'll refrainfor now.Discussion:https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
1 parent1d468b9 commit4526951

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3 files changed

+117
-56
lines changed

3 files changed

+117
-56
lines changed

‎contrib/postgres_fdw/expected/postgres_fdw.out

Lines changed: 15 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -1348,7 +1348,7 @@ SELECT t1.c1, ss.a, ss.b FROM (SELECT c1 FROM ft4 WHERE c1 between 50 and 60) t1
13481348
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
13491349
Foreign Scan
13501350
Output: ft4.c1, ft4_1.c1, ft5.c1
1351-
Relations: (public.ft4) FULL JOIN ((public.ft4) FULL JOIN (public.ft5))
1351+
Relations: (public.ft4) FULL JOIN ((public.ft4 ft4_1) FULL JOIN (public.ft5))
13521352
Remote SQL: SELECT s4.c1, s10.c1, s10.c2 FROM ((SELECT c1 FROM "S 1"."T 3" WHERE ((c1 >= 50)) AND ((c1 <= 60))) s4(c1) FULL JOIN (SELECT s8.c1, s9.c1 FROM ((SELECT c1 FROM "S 1"."T 3" WHERE ((c1 >= 50)) AND ((c1 <= 60))) s8(c1) FULL JOIN (SELECT c1 FROM "S 1"."T 4" WHERE ((c1 >= 50)) AND ((c1 <= 60))) s9(c1) ON (((s8.c1 = s9.c1)))) WHERE (((s8.c1 IS NULL) OR (s8.c1 IS NOT NULL)))) s10(c1, c2) ON (((s4.c1 = s10.c1)))) ORDER BY s4.c1 ASC NULLS LAST, s10.c1 ASC NULLS LAST, s10.c2 ASC NULLS LAST
13531353
(4 rows)
13541354

@@ -2084,7 +2084,7 @@ SELECT t1c1, avg(t1c1 + t2c1) FROM (SELECT t1.c1, t2.c1 FROM ft1 t1 JOIN ft2 t2
20842084
Remote SQL: SELECT r1."C 1", r2."C 1" FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1"))))
20852085
-> Foreign Scan
20862086
Output: t1_1.c1, t2_1.c1
2087-
Relations: (public.ft1t1) INNER JOIN (public.ft2t2)
2087+
Relations: (public.ft1t1_1) INNER JOIN (public.ft2t2_1)
20882088
Remote SQL: SELECT r1."C 1", r2."C 1" FROM ("S 1"."T 1" r1 INNER JOIN "S 1"."T 1" r2 ON (((r1."C 1" = r2."C 1"))))
20892089
(20 rows)
20902090

@@ -3230,7 +3230,7 @@ select count(*), x.b from ft1, (select c2 a, sum(c1) b from ft1 group by c2) x w
32303230
Output: x.b, x.a
32313231
-> Foreign Scan
32323232
Output: ft1_1.c2, (sum(ft1_1.c1))
3233-
Relations: Aggregate on (public.ft1)
3233+
Relations: Aggregate on (public.ft1 ft1_1)
32343234
Remote SQL: SELECT c2, sum("C 1") FROM "S 1"."T 1" GROUP BY 1
32353235
(21 rows)
32363236

@@ -8480,15 +8480,15 @@ ANALYZE fprt2_p2;
84808480
-- inner join three tables
84818481
EXPLAIN (COSTS OFF)
84828482
SELECT t1.a,t2.b,t3.c FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) INNER JOIN fprt1 t3 ON (t2.b = t3.a) WHERE t1.a % 25 =0 ORDER BY 1,2,3;
8483-
QUERY PLAN
8484-
--------------------------------------------------------------------------------------------------------------------
8483+
QUERY PLAN
8484+
--------------------------------------------------------------------------------------------------------------------------
84858485
Sort
84868486
Sort Key: t1.a, t3.c
84878487
-> Append
84888488
-> Foreign Scan
84898489
Relations: ((public.ftprt1_p1 t1) INNER JOIN (public.ftprt2_p1 t2)) INNER JOIN (public.ftprt1_p1 t3)
84908490
-> Foreign Scan
8491-
Relations: ((public.ftprt1_p2t1) INNER JOIN (public.ftprt2_p2t2)) INNER JOIN (public.ftprt1_p2t3)
8491+
Relations: ((public.ftprt1_p2t1_1) INNER JOIN (public.ftprt2_p2t2_1)) INNER JOIN (public.ftprt1_p2t3_1)
84928492
(7 rows)
84938493

84948494
SELECT t1.a,t2.b,t3.c FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) INNER JOIN fprt1 t3 ON (t2.b = t3.a) WHERE t1.a % 25 =0 ORDER BY 1,2,3;
@@ -8507,7 +8507,7 @@ SELECT t1.a,t2.b,t2.c FROM fprt1 t1 LEFT JOIN (SELECT * FROM fprt2 WHERE a < 10)
85078507
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
85088508
Foreign Scan
85098509
Output: t1.a, ftprt2_p1.b, ftprt2_p1.c
8510-
Relations: (public.ftprt1_p1 t1) LEFT JOIN (public.ftprt2_p1 fprt2)
8510+
Relations: (public.ftprt1_p1 t1) LEFT JOIN (public.ftprt2_p1)
85118511
Remote SQL: SELECT r5.a, r6.b, r6.c FROM (public.fprt1_p1 r5 LEFT JOIN public.fprt2_p1 r6 ON (((r5.a = r6.b)) AND ((r5.b = r6.a)) AND ((r6.a < 10)))) WHERE ((r5.a < 10)) ORDER BY r5.a ASC NULLS LAST, r6.b ASC NULLS LAST, r6.c ASC NULLS LAST
85128512
(4 rows)
85138513

@@ -8561,15 +8561,15 @@ SELECT t1.wr, t2.wr FROM (SELECT t1 wr, a FROM fprt1 t1 WHERE t1.a % 25 = 0) t1
85618561
-- join with lateral reference
85628562
EXPLAIN (COSTS OFF)
85638563
SELECT t1.a,t1.b FROM fprt1 t1, LATERAL (SELECT t2.a, t2.b FROM fprt2 t2 WHERE t1.a = t2.b AND t1.b = t2.a) q WHERE t1.a%25 = 0 ORDER BY 1,2;
8564-
QUERY PLAN
8565-
---------------------------------------------------------------------------------
8564+
QUERY PLAN
8565+
-------------------------------------------------------------------------------------
85668566
Sort
85678567
Sort Key: t1.a, t1.b
85688568
-> Append
85698569
-> Foreign Scan
85708570
Relations: (public.ftprt1_p1 t1) INNER JOIN (public.ftprt2_p1 t2)
85718571
-> Foreign Scan
8572-
Relations: (public.ftprt1_p2t1) INNER JOIN (public.ftprt2_p2t2)
8572+
Relations: (public.ftprt1_p2t1_1) INNER JOIN (public.ftprt2_p2t2_1)
85738573
(7 rows)
85748574

85758575
SELECT t1.a,t1.b FROM fprt1 t1, LATERAL (SELECT t2.a, t2.b FROM fprt2 t2 WHERE t1.a = t2.b AND t1.b = t2.a) q WHERE t1.a%25 = 0 ORDER BY 1,2;
@@ -8689,17 +8689,17 @@ SELECT a, sum(b), min(b), count(*) FROM pagg_tab GROUP BY a HAVING avg(b) < 22 O
86898689
SET enable_partitionwise_aggregate TO true;
86908690
EXPLAIN (COSTS OFF)
86918691
SELECT a, sum(b), min(b), count(*) FROM pagg_tab GROUP BY a HAVING avg(b) < 22 ORDER BY 1;
8692-
QUERY PLAN
8693-
----------------------------------------------------------------------
8692+
QUERY PLAN
8693+
-------------------------------------------------------------
86948694
Sort
86958695
Sort Key: fpagg_tab_p1.a
86968696
-> Append
86978697
-> Foreign Scan
8698-
Relations: Aggregate on (public.fpagg_tab_p1 pagg_tab)
8698+
Relations: Aggregate on (public.fpagg_tab_p1)
86998699
-> Foreign Scan
8700-
Relations: Aggregate on (public.fpagg_tab_p2 pagg_tab)
8700+
Relations: Aggregate on (public.fpagg_tab_p2)
87018701
-> Foreign Scan
8702-
Relations: Aggregate on (public.fpagg_tab_p3 pagg_tab)
8702+
Relations: Aggregate on (public.fpagg_tab_p3)
87038703
(9 rows)
87048704

87058705
SELECT a, sum(b), min(b), count(*) FROM pagg_tab GROUP BY a HAVING avg(b) < 22 ORDER BY 1;

‎contrib/postgres_fdw/postgres_fdw.c

Lines changed: 95 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,8 @@
1212
*/
1313
#include"postgres.h"
1414

15+
#include<limits.h>
16+
1517
#include"access/htup_details.h"
1618
#include"access/sysattr.h"
1719
#include"access/table.h"
@@ -574,9 +576,6 @@ postgresGetForeignRelSize(PlannerInfo *root,
574576
PgFdwRelationInfo*fpinfo;
575577
ListCell*lc;
576578
RangeTblEntry*rte=planner_rt_fetch(baserel->relid,root);
577-
constchar*namespace;
578-
constchar*relname;
579-
constchar*refname;
580579

581580
/*
582581
* We use PgFdwRelationInfo to pass various information to subsequent
@@ -719,21 +718,11 @@ postgresGetForeignRelSize(PlannerInfo *root,
719718
}
720719

721720
/*
722-
* Set the name of relation in fpinfo, while we are constructing it here.
723-
* It will be used to build the string describing the join relation in
724-
* EXPLAIN output. We can't know whether VERBOSE option is specified or
725-
* not, so always schema-qualify the foreign table name.
721+
* fpinfo->relation_name gets the numeric rangetable index of the foreign
722+
* table RTE. (If this query gets EXPLAIN'd, we'll convert that to a
723+
* human-readable string at that time.)
726724
*/
727-
fpinfo->relation_name=makeStringInfo();
728-
namespace=get_namespace_name(get_rel_namespace(foreigntableid));
729-
relname=get_rel_name(foreigntableid);
730-
refname=rte->eref->aliasname;
731-
appendStringInfo(fpinfo->relation_name,"%s.%s",
732-
quote_identifier(namespace),
733-
quote_identifier(relname));
734-
if (*refname&&strcmp(refname,relname)!=0)
735-
appendStringInfo(fpinfo->relation_name," %s",
736-
quote_identifier(rte->eref->aliasname));
725+
fpinfo->relation_name=psprintf("%u",baserel->relid);
737726

738727
/* No outer and inner relations. */
739728
fpinfo->make_outerrel_subquery= false;
@@ -1376,7 +1365,7 @@ postgresGetForeignPlan(PlannerInfo *root,
13761365
makeInteger(fpinfo->fetch_size));
13771366
if (IS_JOIN_REL(foreignrel)||IS_UPPER_REL(foreignrel))
13781367
fdw_private=lappend(fdw_private,
1379-
makeString(fpinfo->relation_name->data));
1368+
makeString(fpinfo->relation_name));
13801369

13811370
/*
13821371
* Create the ForeignScan node for the given relation.
@@ -2528,27 +2517,94 @@ postgresEndDirectModify(ForeignScanState *node)
25282517
staticvoid
25292518
postgresExplainForeignScan(ForeignScanState*node,ExplainState*es)
25302519
{
2531-
List*fdw_private;
2532-
char*sql;
2533-
char*relations;
2534-
2535-
fdw_private= ((ForeignScan*)node->ss.ps.plan)->fdw_private;
2520+
ForeignScan*plan=castNode(ForeignScan,node->ss.ps.plan);
2521+
List*fdw_private=plan->fdw_private;
25362522

25372523
/*
2538-
* Add names of relation handled by the foreign scan when the scan is a
2539-
* join
2524+
* Identify foreign scans that are really joins or upper relations. The
2525+
* input looks something like "(1) LEFT JOIN (2)", and we must replace the
2526+
* digit string(s), which are RT indexes, with the correct relation names.
2527+
* We do that here, not when the plan is created, because we can't know
2528+
* what aliases ruleutils.c will assign at plan creation time.
25402529
*/
25412530
if (list_length(fdw_private)>FdwScanPrivateRelations)
25422531
{
2543-
relations=strVal(list_nth(fdw_private,FdwScanPrivateRelations));
2544-
ExplainPropertyText("Relations",relations,es);
2532+
StringInforelations;
2533+
char*rawrelations;
2534+
char*ptr;
2535+
intminrti,
2536+
rtoffset;
2537+
2538+
rawrelations=strVal(list_nth(fdw_private,FdwScanPrivateRelations));
2539+
2540+
/*
2541+
* A difficulty with using a string representation of RT indexes is
2542+
* that setrefs.c won't update the string when flattening the
2543+
* rangetable. To find out what rtoffset was applied, identify the
2544+
* minimum RT index appearing in the string and compare it to the
2545+
* minimum member of plan->fs_relids. (We expect all the relids in
2546+
* the join will have been offset by the same amount; the Asserts
2547+
* below should catch it if that ever changes.)
2548+
*/
2549+
minrti=INT_MAX;
2550+
ptr=rawrelations;
2551+
while (*ptr)
2552+
{
2553+
if (isdigit((unsignedchar)*ptr))
2554+
{
2555+
intrti=strtol(ptr,&ptr,10);
2556+
2557+
if (rti<minrti)
2558+
minrti=rti;
2559+
}
2560+
else
2561+
ptr++;
2562+
}
2563+
rtoffset=bms_next_member(plan->fs_relids,-1)-minrti;
2564+
2565+
/* Now we can translate the string */
2566+
relations=makeStringInfo();
2567+
ptr=rawrelations;
2568+
while (*ptr)
2569+
{
2570+
if (isdigit((unsignedchar)*ptr))
2571+
{
2572+
intrti=strtol(ptr,&ptr,10);
2573+
RangeTblEntry*rte;
2574+
char*namespace;
2575+
char*relname;
2576+
char*refname;
2577+
2578+
rti+=rtoffset;
2579+
Assert(bms_is_member(rti,plan->fs_relids));
2580+
rte=rt_fetch(rti,es->rtable);
2581+
Assert(rte->rtekind==RTE_RELATION);
2582+
/* This logic should agree with explain.c's ExplainTargetRel */
2583+
namespace=get_namespace_name(get_rel_namespace(rte->relid));
2584+
relname=get_rel_name(rte->relid);
2585+
appendStringInfo(relations,"%s.%s",
2586+
quote_identifier(namespace),
2587+
quote_identifier(relname));
2588+
refname= (char*)list_nth(es->rtable_names,rti-1);
2589+
if (refname==NULL)
2590+
refname=rte->eref->aliasname;
2591+
if (strcmp(refname,relname)!=0)
2592+
appendStringInfo(relations," %s",
2593+
quote_identifier(refname));
2594+
}
2595+
else
2596+
appendStringInfoChar(relations,*ptr++);
2597+
}
2598+
ExplainPropertyText("Relations",relations->data,es);
25452599
}
25462600

25472601
/*
25482602
* Add remote query, when VERBOSE option is specified.
25492603
*/
25502604
if (es->verbose)
25512605
{
2606+
char*sql;
2607+
25522608
sql=strVal(list_nth(fdw_private,FdwScanPrivateSelectSql));
25532609
ExplainPropertyText("Remote SQL",sql,es);
25542610
}
@@ -5171,13 +5227,14 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
51715227

51725228
/*
51735229
* Set the string describing this join relation to be used in EXPLAIN
5174-
* output of corresponding ForeignScan.
5230+
* output of corresponding ForeignScan. Note that the decoration we add
5231+
* to the base relation names mustn't include any digits, or it'll confuse
5232+
* postgresExplainForeignScan.
51755233
*/
5176-
fpinfo->relation_name=makeStringInfo();
5177-
appendStringInfo(fpinfo->relation_name,"(%s) %s JOIN (%s)",
5178-
fpinfo_o->relation_name->data,
5179-
get_jointype_name(fpinfo->jointype),
5180-
fpinfo_i->relation_name->data);
5234+
fpinfo->relation_name=psprintf("(%s) %s JOIN (%s)",
5235+
fpinfo_o->relation_name,
5236+
get_jointype_name(fpinfo->jointype),
5237+
fpinfo_i->relation_name);
51815238

51825239
/*
51835240
* Set the relation index. This is defined as the position of this
@@ -5723,11 +5780,12 @@ foreign_grouping_ok(PlannerInfo *root, RelOptInfo *grouped_rel,
57235780

57245781
/*
57255782
* Set the string describing this grouped relation to be used in EXPLAIN
5726-
* output of corresponding ForeignScan.
5783+
* output of corresponding ForeignScan. Note that the decoration we add
5784+
* to the base relation name mustn't include any digits, or it'll confuse
5785+
* postgresExplainForeignScan.
57275786
*/
5728-
fpinfo->relation_name=makeStringInfo();
5729-
appendStringInfo(fpinfo->relation_name,"Aggregate on (%s)",
5730-
ofpinfo->relation_name->data);
5787+
fpinfo->relation_name=psprintf("Aggregate on (%s)",
5788+
ofpinfo->relation_name);
57315789

57325790
return true;
57335791
}

‎contrib/postgres_fdw/postgres_fdw.h

Lines changed: 7 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -87,11 +87,14 @@ typedef struct PgFdwRelationInfo
8787
intfetch_size;/* fetch size for this remote table */
8888

8989
/*
90-
* Name of the relation while EXPLAINing ForeignScan. It is used for join
91-
* relations but is set for all relations. For join relation, the name
92-
* indicates which foreign tables are being joined and the join type used.
90+
* Name of the relation, for use while EXPLAINing ForeignScan. It is used
91+
* for join and upper relations but is set for all relations. For a base
92+
* relation, this is really just the RT index as a string; we convert that
93+
* while producing EXPLAIN output. For join and upper relations, the name
94+
* indicates which base foreign tables are included and the join type or
95+
* aggregation type used.
9396
*/
94-
StringInforelation_name;
97+
char*relation_name;
9598

9699
/* Join information */
97100
RelOptInfo*outerrel;

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