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Commit6b28994

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Redesign PlanForeignScan API to allow multiple paths for a foreign table.
The original API specification only allowed an FDW to create a singleaccess path, which doesn't seem like a terribly good idea in hindsight.Instead, move the responsibility for building the Path node and callingadd_path() into the FDW's PlanForeignScan function. Now, it can do thatmore than once if appropriate. There is no longer any need for thetransient FdwPlan struct, so get rid of that.Etsuro Fujita, Shigeru Hanada, Tom Lane
1 parent3f47e14 commit6b28994

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12 files changed

+103
-125
lines changed

12 files changed

+103
-125
lines changed

‎contrib/file_fdw/file_fdw.c

Lines changed: 30 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -25,6 +25,7 @@
2525
#include"miscadmin.h"
2626
#include"nodes/makefuncs.h"
2727
#include"optimizer/cost.h"
28+
#include"optimizer/pathnode.h"
2829
#include"utils/rel.h"
2930
#include"utils/syscache.h"
3031

@@ -93,7 +94,7 @@ PG_FUNCTION_INFO_V1(file_fdw_validator);
9394
/*
9495
* FDW callback routines
9596
*/
96-
staticFdwPlan*filePlanForeignScan(Oidforeigntableid,
97+
staticvoidfilePlanForeignScan(Oidforeigntableid,
9798
PlannerInfo*root,
9899
RelOptInfo*baserel);
99100
staticvoidfileExplainForeignScan(ForeignScanState*node,ExplainState*es);
@@ -406,27 +407,44 @@ get_file_fdw_attribute_options(Oid relid)
406407

407408
/*
408409
* filePlanForeignScan
409-
*Create a FdwPlan for a scan on the foreign table
410+
*Create possible access paths for a scan on the foreign table
411+
*
412+
*Currently we don't support any push-down feature, so there is only one
413+
*possible access path, which simply returns all records in the order in
414+
*the data file.
410415
*/
411-
staticFdwPlan*
416+
staticvoid
412417
filePlanForeignScan(Oidforeigntableid,
413418
PlannerInfo*root,
414419
RelOptInfo*baserel)
415420
{
416-
FdwPlan*fdwplan;
417421
char*filename;
418422
List*options;
423+
Coststartup_cost;
424+
Costtotal_cost;
419425

420426
/* Fetch options --- we only need filename at this point */
421427
fileGetOptions(foreigntableid,&filename,&options);
422428

423-
/* Construct FdwPlan with cost estimates */
424-
fdwplan=makeNode(FdwPlan);
429+
/* Estimate costs and update baserel->rows */
425430
estimate_costs(root,baserel,filename,
426-
&fdwplan->startup_cost,&fdwplan->total_cost);
427-
fdwplan->fdw_private=NIL;/* not used */
431+
&startup_cost,&total_cost);
432+
433+
/* Create a ForeignPath node and add it as only possible path */
434+
add_path(baserel, (Path*)
435+
create_foreignscan_path(root,baserel,
436+
baserel->rows,
437+
startup_cost,
438+
total_cost,
439+
NIL,/* no pathkeys */
440+
NULL,/* no outer rel either */
441+
NIL,
442+
NIL));/* no fdw_private data */
428443

429-
returnfdwplan;
444+
/*
445+
* If data file was sorted, and we knew it somehow, we could insert
446+
* appropriate pathkeys into the ForeignPath node to tell the planner that.
447+
*/
430448
}
431449

432450
/*
@@ -576,6 +594,9 @@ fileReScanForeignScan(ForeignScanState *node)
576594

577595
/*
578596
* Estimate costs of scanning a foreign table.
597+
*
598+
* In addition to setting *startup_cost and *total_cost, this should
599+
* update baserel->rows.
579600
*/
580601
staticvoid
581602
estimate_costs(PlannerInfo*root,RelOptInfo*baserel,

‎doc/src/sgml/fdwhandler.sgml

Lines changed: 21 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -88,21 +88,31 @@
8888

8989
<para>
9090
<programlisting>
91-
FdwPlan *
91+
void
9292
PlanForeignScan (Oid foreigntableid,
9393
PlannerInfo *root,
9494
RelOptInfo *baserel);
9595
</programlisting>
9696

97-
Plan a scan on a foreign table. This is called when a query is planned.
97+
Create possible access paths for a scan on a foreign table. This is
98+
called when a query is planned.
9899
<literal>foreigntableid</> is the <structname>pg_class</> OID of the
99100
foreign table. <literal>root</> is the planner's global information
100101
about the query, and <literal>baserel</> is the planner's information
101102
about this table.
102-
The function must return a palloc'd struct that contains cost estimates
103-
plus any FDW-private information that is needed to execute the foreign
104-
scan at a later time. (Note that the private information must be
105-
represented in a form that <function>copyObject</> knows how to copy.)
103+
</para>
104+
105+
<para>
106+
The function must generate at least one access path (ForeignPath node)
107+
for a scan on the foreign table and must call <function>add_path</> to
108+
add the path to <literal>baserel-&gt;pathlist</>. It's recommended to
109+
use <function>create_foreignscan_path</> to build the ForeignPath node.
110+
The function may generate multiple access paths, e.g., a path which has
111+
valid <literal>pathkeys</> to represent a pre-sorted result. Each access
112+
path must contain cost estimates, and can contain any FDW-private
113+
information that is needed to execute the foreign scan at a later time.
114+
(Note that the private information must be represented in a form that
115+
<function>copyObject</> knows how to copy.)
106116
</para>
107117

108118
<para>
@@ -159,9 +169,8 @@ BeginForeignScan (ForeignScanState *node,
159169
its <structfield>fdw_state</> field is still NULL. Information about
160170
the table to scan is accessible through the
161171
<structname>ForeignScanState</> node (in particular, from the underlying
162-
<structname>ForeignScan</> plan node, which contains a pointer to the
163-
<structname>FdwPlan</> structure returned by
164-
<function>PlanForeignScan</>).
172+
<structname>ForeignScan</> plan node, which contains any FDW-private
173+
information provided by <function>PlanForeignScan</>).
165174
</para>
166175

167176
<para>
@@ -228,9 +237,9 @@ EndForeignScan (ForeignScanState *node);
228237
</para>
229238

230239
<para>
231-
The <structname>FdwRoutine</>and <structname>FdwPlan</> struct types
232-
are declared in<filename>src/include/foreign/fdwapi.h</>, which see
233-
for additionaldetails.
240+
The <structname>FdwRoutine</>struct type is declared in
241+
<filename>src/include/foreign/fdwapi.h</>, which see for additional
242+
details.
234243
</para>
235244

236245
</sect1>

‎src/backend/nodes/copyfuncs.c

Lines changed: 2 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,8 @@
2323
#include"postgres.h"
2424

2525
#include"miscadmin.h"
26-
#include"foreign/fdwapi.h"
26+
#include"nodes/plannodes.h"
27+
#include"nodes/relation.h"
2728
#include"utils/datum.h"
2829

2930

@@ -591,21 +592,6 @@ _copyForeignScan(const ForeignScan *from)
591592
* copy remainder of node
592593
*/
593594
COPY_SCALAR_FIELD(fsSystemCol);
594-
COPY_NODE_FIELD(fdwplan);
595-
596-
returnnewnode;
597-
}
598-
599-
/*
600-
* _copyFdwPlan
601-
*/
602-
staticFdwPlan*
603-
_copyFdwPlan(constFdwPlan*from)
604-
{
605-
FdwPlan*newnode=makeNode(FdwPlan);
606-
607-
COPY_SCALAR_FIELD(startup_cost);
608-
COPY_SCALAR_FIELD(total_cost);
609595
COPY_NODE_FIELD(fdw_private);
610596

611597
returnnewnode;
@@ -3842,9 +3828,6 @@ copyObject(const void *from)
38423828
caseT_ForeignScan:
38433829
retval=_copyForeignScan(from);
38443830
break;
3845-
caseT_FdwPlan:
3846-
retval=_copyFdwPlan(from);
3847-
break;
38483831
caseT_Join:
38493832
retval=_copyJoin(from);
38503833
break;

‎src/backend/nodes/outfuncs.c

Lines changed: 4 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,9 @@
2323

2424
#include<ctype.h>
2525

26-
#include"foreign/fdwapi.h"
26+
#include"lib/stringinfo.h"
27+
#include"nodes/plannodes.h"
28+
#include"nodes/relation.h"
2729
#include"utils/datum.h"
2830

2931

@@ -558,16 +560,6 @@ _outForeignScan(StringInfo str, const ForeignScan *node)
558560
_outScanInfo(str, (constScan*)node);
559561

560562
WRITE_BOOL_FIELD(fsSystemCol);
561-
WRITE_NODE_FIELD(fdwplan);
562-
}
563-
564-
staticvoid
565-
_outFdwPlan(StringInfostr,constFdwPlan*node)
566-
{
567-
WRITE_NODE_TYPE("FDWPLAN");
568-
569-
WRITE_FLOAT_FIELD(startup_cost,"%.2f");
570-
WRITE_FLOAT_FIELD(total_cost,"%.2f");
571563
WRITE_NODE_FIELD(fdw_private);
572564
}
573565

@@ -1572,7 +1564,7 @@ _outForeignPath(StringInfo str, const ForeignPath *node)
15721564

15731565
_outPathInfo(str, (constPath*)node);
15741566

1575-
WRITE_NODE_FIELD(fdwplan);
1567+
WRITE_NODE_FIELD(fdw_private);
15761568
}
15771569

15781570
staticvoid
@@ -2745,9 +2737,6 @@ _outNode(StringInfo str, const void *obj)
27452737
caseT_ForeignScan:
27462738
_outForeignScan(str,obj);
27472739
break;
2748-
caseT_FdwPlan:
2749-
_outFdwPlan(str,obj);
2750-
break;
27512740
caseT_Join:
27522741
_outJoin(str,obj);
27532742
break;

‎src/backend/optimizer/path/allpaths.c

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@
1818
#include<math.h>
1919

2020
#include"catalog/pg_class.h"
21+
#include"foreign/fdwapi.h"
2122
#include"nodes/nodeFuncs.h"
2223
#ifdefOPTIMIZER_DEBUG
2324
#include"nodes/print.h"
@@ -399,15 +400,18 @@ set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
399400

400401
/*
401402
* set_foreign_pathlist
402-
*Buildthe (single)accesspath for a foreign table RTE
403+
*Build accesspaths for a foreign table RTE
403404
*/
404405
staticvoid
405406
set_foreign_pathlist(PlannerInfo*root,RelOptInfo*rel,RangeTblEntry*rte)
406407
{
407-
/* Generate appropriate path */
408-
add_path(rel, (Path*)create_foreignscan_path(root,rel));
408+
FdwRoutine*fdwroutine;
409409

410-
/* Select cheapest path (pretty easy in this case...) */
410+
/* Call the FDW's PlanForeignScan function to generate path(s) */
411+
fdwroutine=GetFdwRoutineByRelId(rte->relid);
412+
fdwroutine->PlanForeignScan(rte->relid,root,rel);
413+
414+
/* Select cheapest path */
411415
set_cheapest(rel);
412416
}
413417

‎src/backend/optimizer/plan/createplan.c

Lines changed: 4 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,6 @@
2020
#include<math.h>
2121

2222
#include"access/skey.h"
23-
#include"foreign/fdwapi.h"
2423
#include"miscadmin.h"
2524
#include"nodes/makefuncs.h"
2625
#include"nodes/nodeFuncs.h"
@@ -121,7 +120,7 @@ static CteScan *make_ctescan(List *qptlist, List *qpqual,
121120
staticWorkTableScan*make_worktablescan(List*qptlist,List*qpqual,
122121
Indexscanrelid,intwtParam);
123122
staticForeignScan*make_foreignscan(List*qptlist,List*qpqual,
124-
Indexscanrelid,boolfsSystemCol,FdwPlan*fdwplan);
123+
Indexscanrelid,boolfsSystemCol,List*fdw_private);
125124
staticBitmapAnd*make_bitmap_and(List*bitmapplans);
126125
staticBitmapOr*make_bitmap_or(List*bitmapplans);
127126
staticNestLoop*make_nestloop(List*tlist,
@@ -1847,7 +1846,7 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
18471846
scan_clauses,
18481847
scan_relid,
18491848
fsSystemCol,
1850-
best_path->fdwplan);
1849+
best_path->fdw_private);
18511850

18521851
copy_path_costsize(&scan_plan->scan.plan,&best_path->path);
18531852

@@ -3189,7 +3188,7 @@ make_foreignscan(List *qptlist,
31893188
List*qpqual,
31903189
Indexscanrelid,
31913190
boolfsSystemCol,
3192-
FdwPlan*fdwplan)
3191+
List*fdw_private)
31933192
{
31943193
ForeignScan*node=makeNode(ForeignScan);
31953194
Plan*plan=&node->scan.plan;
@@ -3201,7 +3200,7 @@ make_foreignscan(List *qptlist,
32013200
plan->righttree=NULL;
32023201
node->scan.scanrelid=scanrelid;
32033202
node->fsSystemCol=fsSystemCol;
3204-
node->fdwplan=fdwplan;
3203+
node->fdw_private=fdw_private;
32053204

32063205
returnnode;
32073206
}

‎src/backend/optimizer/util/pathnode.c

Lines changed: 17 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@
1616

1717
#include<math.h>
1818

19-
#include"foreign/fdwapi.h"
2019
#include"miscadmin.h"
2120
#include"nodes/nodeFuncs.h"
2221
#include"optimizer/clauses.h"
@@ -1766,36 +1765,31 @@ create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel)
17661765
* create_foreignscan_path
17671766
* Creates a path corresponding to a scan of a foreign table,
17681767
* returning the pathnode.
1768+
*
1769+
* This function is never called from core Postgres; rather, it's expected
1770+
* to be called by the PlanForeignScan function of a foreign data wrapper.
1771+
* We make the FDW supply all fields of the path, since we do not have any
1772+
* way to calculate them in core.
17691773
*/
17701774
ForeignPath*
1771-
create_foreignscan_path(PlannerInfo*root,RelOptInfo*rel)
1775+
create_foreignscan_path(PlannerInfo*root,RelOptInfo*rel,
1776+
doublerows,Coststartup_cost,Costtotal_cost,
1777+
List*pathkeys,
1778+
Relidsrequired_outer,List*param_clauses,
1779+
List*fdw_private)
17721780
{
17731781
ForeignPath*pathnode=makeNode(ForeignPath);
1774-
RangeTblEntry*rte;
1775-
FdwRoutine*fdwroutine;
1776-
FdwPlan*fdwplan;
17771782

17781783
pathnode->path.pathtype=T_ForeignScan;
17791784
pathnode->path.parent=rel;
1780-
pathnode->path.pathkeys=NIL;/* result is always unordered */
1781-
pathnode->path.required_outer=NULL;
1782-
pathnode->path.param_clauses=NIL;
1785+
pathnode->path.rows=rows;
1786+
pathnode->path.startup_cost=startup_cost;
1787+
pathnode->path.total_cost=total_cost;
1788+
pathnode->path.pathkeys=pathkeys;
1789+
pathnode->path.required_outer=required_outer;
1790+
pathnode->path.param_clauses=param_clauses;
17831791

1784-
/* Get FDW's callback info */
1785-
rte=planner_rt_fetch(rel->relid,root);
1786-
fdwroutine=GetFdwRoutineByRelId(rte->relid);
1787-
1788-
/* Let the FDW do its planning */
1789-
fdwplan=fdwroutine->PlanForeignScan(rte->relid,root,rel);
1790-
if (fdwplan==NULL|| !IsA(fdwplan,FdwPlan))
1791-
elog(ERROR,"foreign-data wrapper PlanForeignScan function for relation %u did not return an FdwPlan struct",
1792-
rte->relid);
1793-
pathnode->fdwplan=fdwplan;
1794-
1795-
/* use costs estimated by FDW */
1796-
pathnode->path.rows=rel->rows;
1797-
pathnode->path.startup_cost=fdwplan->startup_cost;
1798-
pathnode->path.total_cost=fdwplan->total_cost;
1792+
pathnode->fdw_private=fdw_private;
17991793

18001794
returnpathnode;
18011795
}

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