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nodeForeignscan.c
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1 /*-------------------------------------------------------------------------
2  *
3  * nodeForeignscan.c
4  * Routines to support scans of foreign tables
5  *
6  * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  *
10  * IDENTIFICATION
11  * src/backend/executor/nodeForeignscan.c
12  *
13  *-------------------------------------------------------------------------
14  */
15 /*
16  * INTERFACE ROUTINES
17  *
18  * ExecForeignScan scans a foreign table.
19  * ExecInitForeignScan creates and initializes state info.
20  * ExecReScanForeignScan rescans the foreign relation.
21  * ExecEndForeignScan releases any resources allocated.
22  */
23 #include "postgres.h"
24 
25 #include "executor/executor.h"
27 #include "foreign/fdwapi.h"
28 #include "utils/memutils.h"
29 #include "utils/rel.h"
30 
32 static bool ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot);
33 
34 
35 /* ----------------------------------------------------------------
36  * ForeignNext
37  *
38  * This is a workhorse for ExecForeignScan
39  * ----------------------------------------------------------------
40  */
41 static TupleTableSlot *
43 {
44  TupleTableSlot *slot;
45  ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
46  ExprContext *econtext = node->ss.ps.ps_ExprContext;
47  MemoryContext oldcontext;
48 
49  /* Call the Iterate function in short-lived context */
50  oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
51  if (plan->operation != CMD_SELECT)
52  slot = node->fdwroutine->IterateDirectModify(node);
53  else
54  slot = node->fdwroutine->IterateForeignScan(node);
55  MemoryContextSwitchTo(oldcontext);
56 
57  /*
58  * If any system columns are requested, we have to force the tuple into
59  * physical-tuple form to avoid "cannot extract system attribute from
60  * virtual tuple" errors later. We also insert a valid value for
61  * tableoid, which is the only actually-useful system column.
62  */
63  if (plan->fsSystemCol && !TupIsNull(slot))
64  {
65  HeapTuple tup = ExecMaterializeSlot(slot);
66 
68  }
69 
70  return slot;
71 }
72 
73 /*
74  * ForeignRecheck -- access method routine to recheck a tuple in EvalPlanQual
75  */
76 static bool
78 {
79  FdwRoutine *fdwroutine = node->fdwroutine;
80  ExprContext *econtext;
81 
82  /*
83  * extract necessary information from foreign scan node
84  */
85  econtext = node->ss.ps.ps_ExprContext;
86 
87  /* Does the tuple meet the remote qual condition? */
88  econtext->ecxt_scantuple = slot;
89 
90  ResetExprContext(econtext);
91 
92  /*
93  * If an outer join is pushed down, RecheckForeignScan may need to store a
94  * different tuple in the slot, because a different set of columns may go
95  * to NULL upon recheck. Otherwise, it shouldn't need to change the slot
96  * contents, just return true or false to indicate whether the quals still
97  * pass. For simple cases, setting fdw_recheck_quals may be easier than
98  * providing this callback.
99  */
100  if (fdwroutine->RecheckForeignScan &&
101  !fdwroutine->RecheckForeignScan(node, slot))
102  return false;
103 
104  return ExecQual(node->fdw_recheck_quals, econtext);
105 }
106 
107 /* ----------------------------------------------------------------
108  * ExecForeignScan(node)
109  *
110  * Fetches the next tuple from the FDW, checks local quals, and
111  * returns it.
112  * We call the ExecScan() routine and pass it the appropriate
113  * access method functions.
114  * ----------------------------------------------------------------
115  */
116 static TupleTableSlot *
118 {
119  ForeignScanState *node = castNode(ForeignScanState, pstate);
120 
121  return ExecScan(&node->ss,
124 }
125 
126 
127 /* ----------------------------------------------------------------
128  * ExecInitForeignScan
129  * ----------------------------------------------------------------
130  */
132 ExecInitForeignScan(ForeignScan *node, EState *estate, int eflags)
133 {
134  ForeignScanState *scanstate;
135  Relation currentRelation = NULL;
136  Index scanrelid = node->scan.scanrelid;
137  Index tlistvarno;
138  FdwRoutine *fdwroutine;
139 
140  /* check for unsupported flags */
141  Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
142 
143  /*
144  * create state structure
145  */
146  scanstate = makeNode(ForeignScanState);
147  scanstate->ss.ps.plan = (Plan *) node;
148  scanstate->ss.ps.state = estate;
149  scanstate->ss.ps.ExecProcNode = ExecForeignScan;
150 
151  /*
152  * Miscellaneous initialization
153  *
154  * create expression context for node
155  */
156  ExecAssignExprContext(estate, &scanstate->ss.ps);
157 
158  /*
159  * open the base relation, if any, and acquire an appropriate lock on it;
160  * also acquire function pointers from the FDW's handler
161  */
162  if (scanrelid > 0)
163  {
164  currentRelation = ExecOpenScanRelation(estate, scanrelid, eflags);
165  scanstate->ss.ss_currentRelation = currentRelation;
166  fdwroutine = GetFdwRoutineForRelation(currentRelation, true);
167  }
168  else
169  {
170  /* We can't use the relcache, so get fdwroutine the hard way */
171  fdwroutine = GetFdwRoutineByServerId(node->fs_server);
172  }
173 
174  /*
175  * Determine the scan tuple type. If the FDW provided a targetlist
176  * describing the scan tuples, use that; else use base relation's rowtype.
177  */
178  if (node->fdw_scan_tlist != NIL || currentRelation == NULL)
179  {
180  TupleDesc scan_tupdesc;
181 
182  scan_tupdesc = ExecTypeFromTL(node->fdw_scan_tlist, false);
183  ExecInitScanTupleSlot(estate, &scanstate->ss, scan_tupdesc);
184  /* Node's targetlist will contain Vars with varno = INDEX_VAR */
185  tlistvarno = INDEX_VAR;
186  }
187  else
188  {
189  TupleDesc scan_tupdesc;
190 
191  /* don't trust FDWs to return tuples fulfilling NOT NULL constraints */
192  scan_tupdesc = CreateTupleDescCopy(RelationGetDescr(currentRelation));
193  ExecInitScanTupleSlot(estate, &scanstate->ss, scan_tupdesc);
194  /* Node's targetlist will contain Vars with varno = scanrelid */
195  tlistvarno = scanrelid;
196  }
197 
198  /*
199  * Initialize result slot, type and projection.
200  */
201  ExecInitResultTupleSlotTL(estate, &scanstate->ss.ps);
202  ExecAssignScanProjectionInfoWithVarno(&scanstate->ss, tlistvarno);
203 
204  /*
205  * initialize child expressions
206  */
207  scanstate->ss.ps.qual =
208  ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
209  scanstate->fdw_recheck_quals =
210  ExecInitQual(node->fdw_recheck_quals, (PlanState *) scanstate);
211 
212  /*
213  * Initialize FDW-related state.
214  */
215  scanstate->fdwroutine = fdwroutine;
216  scanstate->fdw_state = NULL;
217 
218  /* Initialize any outer plan. */
219  if (outerPlan(node))
220  outerPlanState(scanstate) =
221  ExecInitNode(outerPlan(node), estate, eflags);
222 
223  /*
224  * Tell the FDW to initialize the scan.
225  */
226  if (node->operation != CMD_SELECT)
227  fdwroutine->BeginDirectModify(scanstate, eflags);
228  else
229  fdwroutine->BeginForeignScan(scanstate, eflags);
230 
231  return scanstate;
232 }
233 
234 /* ----------------------------------------------------------------
235  * ExecEndForeignScan
236  *
237  * frees any storage allocated through C routines.
238  * ----------------------------------------------------------------
239  */
240 void
242 {
243  ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
244 
245  /* Let the FDW shut down */
246  if (plan->operation != CMD_SELECT)
247  node->fdwroutine->EndDirectModify(node);
248  else
249  node->fdwroutine->EndForeignScan(node);
250 
251  /* Shut down any outer plan. */
252  if (outerPlanState(node))
254 
255  /* Free the exprcontext */
256  ExecFreeExprContext(&node->ss.ps);
257 
258  /* clean out the tuple table */
261 
262  /* close the relation. */
263  if (node->ss.ss_currentRelation)
265 }
266 
267 /* ----------------------------------------------------------------
268  * ExecReScanForeignScan
269  *
270  * Rescans the relation.
271  * ----------------------------------------------------------------
272  */
273 void
275 {
277 
278  node->fdwroutine->ReScanForeignScan(node);
279 
280  /*
281  * If chgParam of subnode is not null then plan will be re-scanned by
282  * first ExecProcNode. outerPlan may also be NULL, in which case there is
283  * nothing to rescan at all.
284  */
285  if (outerPlan != NULL && outerPlan->chgParam == NULL)
286  ExecReScan(outerPlan);
287 
288  ExecScanReScan(&node->ss);
289 }
290 
291 /* ----------------------------------------------------------------
292  * ExecForeignScanEstimate
293  *
294  * Informs size of the parallel coordination information, if any
295  * ----------------------------------------------------------------
296  */
297 void
299 {
300  FdwRoutine *fdwroutine = node->fdwroutine;
301 
302  if (fdwroutine->EstimateDSMForeignScan)
303  {
304  node->pscan_len = fdwroutine->EstimateDSMForeignScan(node, pcxt);
306  shm_toc_estimate_keys(&pcxt->estimator, 1);
307  }
308 }
309 
310 /* ----------------------------------------------------------------
311  * ExecForeignScanInitializeDSM
312  *
313  * Initialize the parallel coordination information
314  * ----------------------------------------------------------------
315  */
316 void
318 {
319  FdwRoutine *fdwroutine = node->fdwroutine;
320 
321  if (fdwroutine->InitializeDSMForeignScan)
322  {
323  int plan_node_id = node->ss.ps.plan->plan_node_id;
324  void *coordinate;
325 
326  coordinate = shm_toc_allocate(pcxt->toc, node->pscan_len);
327  fdwroutine->InitializeDSMForeignScan(node, pcxt, coordinate);
328  shm_toc_insert(pcxt->toc, plan_node_id, coordinate);
329  }
330 }
331 
332 /* ----------------------------------------------------------------
333  * ExecForeignScanReInitializeDSM
334  *
335  * Reset shared state before beginning a fresh scan.
336  * ----------------------------------------------------------------
337  */
338 void
340 {
341  FdwRoutine *fdwroutine = node->fdwroutine;
342 
343  if (fdwroutine->ReInitializeDSMForeignScan)
344  {
345  int plan_node_id = node->ss.ps.plan->plan_node_id;
346  void *coordinate;
347 
348  coordinate = shm_toc_lookup(pcxt->toc, plan_node_id, false);
349  fdwroutine->ReInitializeDSMForeignScan(node, pcxt, coordinate);
350  }
351 }
352 
353 /* ----------------------------------------------------------------
354  * ExecForeignScanInitializeWorker
355  *
356  * Initialization according to the parallel coordination information
357  * ----------------------------------------------------------------
358  */
359 void
361  ParallelWorkerContext *pwcxt)
362 {
363  FdwRoutine *fdwroutine = node->fdwroutine;
364 
365  if (fdwroutine->InitializeWorkerForeignScan)
366  {
367  int plan_node_id = node->ss.ps.plan->plan_node_id;
368  void *coordinate;
369 
370  coordinate = shm_toc_lookup(pwcxt->toc, plan_node_id, false);
371  fdwroutine->InitializeWorkerForeignScan(node, pwcxt->toc, coordinate);
372  }
373 }
374 
375 /* ----------------------------------------------------------------
376  * ExecShutdownForeignScan
377  *
378  * Gives FDW chance to stop asynchronous resource consumption
379  * and release any resources still held.
380  * ----------------------------------------------------------------
381  */
382 void
384 {
385  FdwRoutine *fdwroutine = node->fdwroutine;
386 
387  if (fdwroutine->ShutdownForeignScan)
388  fdwroutine->ShutdownForeignScan(node);
389 }
void ExecForeignScanInitializeWorker(ForeignScanState *node, ParallelWorkerContext *pwcxt)
BeginForeignScan_function BeginForeignScan
Definition: fdwapi.h:190
EndDirectModify_function EndDirectModify
Definition: fdwapi.h:220
#define NIL
Definition: pg_list.h:69
ScanState ss
Definition: execnodes.h:1641
List * qual
Definition: plannodes.h:147
TupleDesc CreateTupleDescCopy(TupleDesc tupdesc)
Definition: tupdesc.c:112
Plan plan
Definition: plannodes.h:342
EstimateDSMForeignScan_function EstimateDSMForeignScan
Definition: fdwapi.h:240
Index scanrelid
Definition: plannodes.h:343
Oid fs_server
Definition: plannodes.h:613
#define RelationGetDescr(relation)
Definition: rel.h:433
#define castNode(_type_, nodeptr)
Definition: nodes.h:586
void ExecEndNode(PlanState *node)
Definition: execProcnode.c:538
InitializeWorkerForeignScan_function InitializeWorkerForeignScan
Definition: fdwapi.h:243
TupleTableSlot * ExecScan(ScanState *node, ExecScanAccessMtd accessMtd, ExecScanRecheckMtd recheckMtd)
Definition: execScan.c:121
ExprContext * ps_ExprContext
Definition: execnodes.h:947
shm_toc_estimator estimator
Definition: parallel.h:41
void ExecReScan(PlanState *node)
Definition: execAmi.c:76
TupleTableSlot * ExecClearTuple(TupleTableSlot *slot)
Definition: execTuples.c:475
int plan_node_id
Definition: plannodes.h:145
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
Definition: palloc.h:109
static bool ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot)
FdwRoutine * GetFdwRoutineByServerId(Oid serverid)
Definition: foreign.c:330
static TupleTableSlot * ExecForeignScan(PlanState *pstate)
TupleTableSlot * ss_ScanTupleSlot
Definition: execnodes.h:1195
List * fdw_scan_tlist
Definition: plannodes.h:616
Relation ss_currentRelation
Definition: execnodes.h:1193
EState * state
Definition: execnodes.h:914
ExprState * fdw_recheck_quals
Definition: execnodes.h:1642
static bool ExecQual(ExprState *state, ExprContext *econtext)
Definition: executor.h:361
#define shm_toc_estimate_chunk(e, sz)
Definition: shm_toc.h:51
void ExecFreeExprContext(PlanState *planstate)
Definition: execUtils.c:566
CmdType operation
Definition: plannodes.h:612
ExprState * ExecInitQual(List *qual, PlanState *parent)
Definition: execExpr.c:205
void ExecReScanForeignScan(ForeignScanState *node)
void ExecForeignScanReInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
RecheckForeignScan_function RecheckForeignScan
Definition: fdwapi.h:225
IterateDirectModify_function IterateDirectModify
Definition: fdwapi.h:219
void ExecAssignScanProjectionInfoWithVarno(ScanState *node, Index varno)
Definition: execScan.c:248
PlanState ps
Definition: execnodes.h:1192
TupleTableSlot * ps_ResultTupleSlot
Definition: execnodes.h:946
Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags)
Definition: execUtils.c:643
void ExecEndForeignScan(ForeignScanState *node)
#define EXEC_FLAG_BACKWARD
Definition: executor.h:60
#define outerPlanState(node)
Definition: execnodes.h:966
EndForeignScan_function EndForeignScan
Definition: fdwapi.h:193
#define TupIsNull(slot)
Definition: tuptable.h:146
struct FdwRoutine * fdwroutine
Definition: execnodes.h:1645
Oid t_tableOid
Definition: htup.h:66
List * fdw_recheck_quals
Definition: plannodes.h:617
Bitmapset * chgParam
Definition: execnodes.h:941
TupleDesc ExecTypeFromTL(List *targetList, bool hasoid)
Definition: execTuples.c:965
#define outerPlan(node)
Definition: plannodes.h:176
bool(* ExecScanRecheckMtd)(ScanState *node, TupleTableSlot *slot)
Definition: executor.h:422
static TupleTableSlot * ForeignNext(ForeignScanState *node)
BeginDirectModify_function BeginDirectModify
Definition: fdwapi.h:218
ExecProcNodeMtd ExecProcNode
Definition: execnodes.h:918
void ExecForeignScanInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
unsigned int Index
Definition: c.h:442
void ExecInitResultTupleSlotTL(EState *estate, PlanState *planstate)
Definition: execTuples.c:890
InitializeDSMForeignScan_function InitializeDSMForeignScan
Definition: fdwapi.h:241
Plan * plan
Definition: execnodes.h:912
#define makeNode(_type_)
Definition: nodes.h:565
#define Assert(condition)
Definition: c.h:699
ReScanForeignScan_function ReScanForeignScan
Definition: fdwapi.h:192
#define EXEC_FLAG_MARK
Definition: executor.h:61
IterateForeignScan_function IterateForeignScan
Definition: fdwapi.h:191
void ExecForeignScanEstimate(ForeignScanState *node, ParallelContext *pcxt)
void ExecAssignExprContext(EState *estate, PlanState *planstate)
Definition: execUtils.c:428
#define shm_toc_estimate_keys(e, cnt)
Definition: shm_toc.h:53
void ExecCloseScanRelation(Relation scanrel)
Definition: execUtils.c:701
TupleTableSlot * ecxt_scantuple
Definition: execnodes.h:218
void * shm_toc_allocate(shm_toc *toc, Size nbytes)
Definition: shm_toc.c:88
HeapTuple ExecMaterializeSlot(TupleTableSlot *slot)
Definition: execTuples.c:781
ExprState * qual
Definition: execnodes.h:930
ReInitializeDSMForeignScan_function ReInitializeDSMForeignScan
Definition: fdwapi.h:242
ShutdownForeignScan_function ShutdownForeignScan
Definition: fdwapi.h:244
void shm_toc_insert(shm_toc *toc, uint64 key, void *address)
Definition: shm_toc.c:171
ForeignScanState * ExecInitForeignScan(ForeignScan *node, EState *estate, int eflags)
FdwRoutine * GetFdwRoutineForRelation(Relation relation, bool makecopy)
Definition: foreign.c:395
void ExecScanReScan(ScanState *node)
Definition: execScan.c:262
void ExecShutdownForeignScan(ForeignScanState *node)
void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate, TupleDesc tupledesc)
Definition: execTuples.c:915
TupleTableSlot *(* ExecScanAccessMtd)(ScanState *node)
Definition: executor.h:421
#define INDEX_VAR
Definition: primnodes.h:156
PlanState * ExecInitNode(Plan *node, EState *estate, int eflags)
Definition: execProcnode.c:139
#define RelationGetRelid(relation)
Definition: rel.h:407
void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError)
Definition: shm_toc.c:232
#define ResetExprContext(econtext)
Definition: executor.h:483
shm_toc * toc
Definition: parallel.h:44
bool fsSystemCol
Definition: plannodes.h:619