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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) 1996-2017, 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  * initialize child expressions
160  */
161  scanstate->ss.ps.qual =
162  ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
163  scanstate->fdw_recheck_quals =
164  ExecInitQual(node->fdw_recheck_quals, (PlanState *) scanstate);
165 
166  /*
167  * tuple table initialization
168  */
169  ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
170  ExecInitScanTupleSlot(estate, &scanstate->ss);
171 
172  /*
173  * open the base relation, if any, and acquire an appropriate lock on it;
174  * also acquire function pointers from the FDW's handler
175  */
176  if (scanrelid > 0)
177  {
178  currentRelation = ExecOpenScanRelation(estate, scanrelid, eflags);
179  scanstate->ss.ss_currentRelation = currentRelation;
180  fdwroutine = GetFdwRoutineForRelation(currentRelation, true);
181  }
182  else
183  {
184  /* We can't use the relcache, so get fdwroutine the hard way */
185  fdwroutine = GetFdwRoutineByServerId(node->fs_server);
186  }
187 
188  /*
189  * Determine the scan tuple type. If the FDW provided a targetlist
190  * describing the scan tuples, use that; else use base relation's rowtype.
191  */
192  if (node->fdw_scan_tlist != NIL || currentRelation == NULL)
193  {
194  TupleDesc scan_tupdesc;
195 
196  scan_tupdesc = ExecTypeFromTL(node->fdw_scan_tlist, false);
197  ExecAssignScanType(&scanstate->ss, scan_tupdesc);
198  /* Node's targetlist will contain Vars with varno = INDEX_VAR */
199  tlistvarno = INDEX_VAR;
200  }
201  else
202  {
203  ExecAssignScanType(&scanstate->ss, RelationGetDescr(currentRelation));
204  /* Node's targetlist will contain Vars with varno = scanrelid */
205  tlistvarno = scanrelid;
206  }
207 
208  /*
209  * Initialize result tuple type and projection info.
210  */
211  ExecAssignResultTypeFromTL(&scanstate->ss.ps);
212  ExecAssignScanProjectionInfoWithVarno(&scanstate->ss, tlistvarno);
213 
214  /*
215  * Initialize FDW-related state.
216  */
217  scanstate->fdwroutine = fdwroutine;
218  scanstate->fdw_state = NULL;
219 
220  /* Initialize any outer plan. */
221  if (outerPlan(node))
222  outerPlanState(scanstate) =
223  ExecInitNode(outerPlan(node), estate, eflags);
224 
225  /*
226  * Tell the FDW to initialize the scan.
227  */
228  if (node->operation != CMD_SELECT)
229  fdwroutine->BeginDirectModify(scanstate, eflags);
230  else
231  fdwroutine->BeginForeignScan(scanstate, eflags);
232 
233  return scanstate;
234 }
235 
236 /* ----------------------------------------------------------------
237  * ExecEndForeignScan
238  *
239  * frees any storage allocated through C routines.
240  * ----------------------------------------------------------------
241  */
242 void
244 {
245  ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
246 
247  /* Let the FDW shut down */
248  if (plan->operation != CMD_SELECT)
249  node->fdwroutine->EndDirectModify(node);
250  else
251  node->fdwroutine->EndForeignScan(node);
252 
253  /* Shut down any outer plan. */
254  if (outerPlanState(node))
256 
257  /* Free the exprcontext */
258  ExecFreeExprContext(&node->ss.ps);
259 
260  /* clean out the tuple table */
263 
264  /* close the relation. */
265  if (node->ss.ss_currentRelation)
267 }
268 
269 /* ----------------------------------------------------------------
270  * ExecReScanForeignScan
271  *
272  * Rescans the relation.
273  * ----------------------------------------------------------------
274  */
275 void
277 {
279 
280  node->fdwroutine->ReScanForeignScan(node);
281 
282  /*
283  * If chgParam of subnode is not null then plan will be re-scanned by
284  * first ExecProcNode. outerPlan may also be NULL, in which case there is
285  * nothing to rescan at all.
286  */
287  if (outerPlan != NULL && outerPlan->chgParam == NULL)
288  ExecReScan(outerPlan);
289 
290  ExecScanReScan(&node->ss);
291 }
292 
293 /* ----------------------------------------------------------------
294  * ExecForeignScanEstimate
295  *
296  * Informs size of the parallel coordination information, if any
297  * ----------------------------------------------------------------
298  */
299 void
301 {
302  FdwRoutine *fdwroutine = node->fdwroutine;
303 
304  if (fdwroutine->EstimateDSMForeignScan)
305  {
306  node->pscan_len = fdwroutine->EstimateDSMForeignScan(node, pcxt);
308  shm_toc_estimate_keys(&pcxt->estimator, 1);
309  }
310 }
311 
312 /* ----------------------------------------------------------------
313  * ExecForeignScanInitializeDSM
314  *
315  * Initialize the parallel coordination information
316  * ----------------------------------------------------------------
317  */
318 void
320 {
321  FdwRoutine *fdwroutine = node->fdwroutine;
322 
323  if (fdwroutine->InitializeDSMForeignScan)
324  {
325  int plan_node_id = node->ss.ps.plan->plan_node_id;
326  void *coordinate;
327 
328  coordinate = shm_toc_allocate(pcxt->toc, node->pscan_len);
329  fdwroutine->InitializeDSMForeignScan(node, pcxt, coordinate);
330  shm_toc_insert(pcxt->toc, plan_node_id, coordinate);
331  }
332 }
333 
334 /* ----------------------------------------------------------------
335  * ExecForeignScanReInitializeDSM
336  *
337  * Reset shared state before beginning a fresh scan.
338  * ----------------------------------------------------------------
339  */
340 void
342 {
343  FdwRoutine *fdwroutine = node->fdwroutine;
344 
345  if (fdwroutine->ReInitializeDSMForeignScan)
346  {
347  int plan_node_id = node->ss.ps.plan->plan_node_id;
348  void *coordinate;
349 
350  coordinate = shm_toc_lookup(pcxt->toc, plan_node_id, false);
351  fdwroutine->ReInitializeDSMForeignScan(node, pcxt, coordinate);
352  }
353 }
354 
355 /* ----------------------------------------------------------------
356  * ExecForeignScanInitializeWorker
357  *
358  * Initialization according to the parallel coordination information
359  * ----------------------------------------------------------------
360  */
361 void
363 {
364  FdwRoutine *fdwroutine = node->fdwroutine;
365 
366  if (fdwroutine->InitializeWorkerForeignScan)
367  {
368  int plan_node_id = node->ss.ps.plan->plan_node_id;
369  void *coordinate;
370 
371  coordinate = shm_toc_lookup(toc, plan_node_id, false);
372  fdwroutine->InitializeWorkerForeignScan(node, toc, coordinate);
373  }
374 }
375 
376 /* ----------------------------------------------------------------
377  * ExecShutdownForeignScan
378  *
379  * Gives FDW chance to stop asynchronous resource consumption
380  * and release any resources still held.
381  * ----------------------------------------------------------------
382  */
383 void
385 {
386  FdwRoutine *fdwroutine = node->fdwroutine;
387 
388  if (fdwroutine->ShutdownForeignScan)
389  fdwroutine->ShutdownForeignScan(node);
390 }
BeginForeignScan_function BeginForeignScan
Definition: fdwapi.h:183
EndDirectModify_function EndDirectModify
Definition: fdwapi.h:211
#define NIL
Definition: pg_list.h:69
ScanState ss
Definition: execnodes.h:1544
List * qual
Definition: plannodes.h:145
Plan plan
Definition: plannodes.h:328
EstimateDSMForeignScan_function EstimateDSMForeignScan
Definition: fdwapi.h:231
void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate)
Definition: execTuples.c:842
Index scanrelid
Definition: plannodes.h:329
Oid fs_server
Definition: plannodes.h:599
#define RelationGetDescr(relation)
Definition: rel.h:428
#define castNode(_type_, nodeptr)
Definition: nodes.h:579
void ExecEndNode(PlanState *node)
Definition: execProcnode.c:523
InitializeWorkerForeignScan_function InitializeWorkerForeignScan
Definition: fdwapi.h:234
TupleTableSlot * ExecScan(ScanState *node, ExecScanAccessMtd accessMtd, ExecScanRecheckMtd recheckMtd)
Definition: execScan.c:123
ExprContext * ps_ExprContext
Definition: execnodes.h:881
shm_toc_estimator estimator
Definition: parallel.h:41
void ExecReScan(PlanState *node)
Definition: execAmi.c:76
TupleTableSlot * ExecClearTuple(TupleTableSlot *slot)
Definition: execTuples.c:439
int plan_node_id
Definition: plannodes.h:143
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:1104
List * fdw_scan_tlist
Definition: plannodes.h:602
Relation ss_currentRelation
Definition: execnodes.h:1102
EState * state
Definition: execnodes.h:849
ExprState * fdw_recheck_quals
Definition: execnodes.h:1545
static bool ExecQual(ExprState *state, ExprContext *econtext)
Definition: executor.h:366
#define shm_toc_estimate_chunk(e, sz)
Definition: shm_toc.h:51
void ExecFreeExprContext(PlanState *planstate)
Definition: execUtils.c:521
CmdType operation
Definition: plannodes.h:598
ExprState * ExecInitQual(List *qual, PlanState *parent)
Definition: execExpr.c:160
void ExecAssignResultTypeFromTL(PlanState *planstate)
Definition: execUtils.c:445
void ExecReScanForeignScan(ForeignScanState *node)
void ExecForeignScanReInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
TupleTableSlot *(* ExecScanAccessMtd)(ScanState *node)
Definition: executor.h:410
RecheckForeignScan_function RecheckForeignScan
Definition: fdwapi.h:216
IterateDirectModify_function IterateDirectModify
Definition: fdwapi.h:210
void ExecAssignScanProjectionInfoWithVarno(ScanState *node, Index varno)
Definition: execScan.c:249
PlanState ps
Definition: execnodes.h:1101
bool(* ExecScanRecheckMtd)(ScanState *node, TupleTableSlot *slot)
Definition: executor.h:411
TupleTableSlot * ps_ResultTupleSlot
Definition: execnodes.h:880
void ExecInitResultTupleSlot(EState *estate, PlanState *planstate)
Definition: execTuples.c:832
Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags)
Definition: execUtils.c:608
void ExecEndForeignScan(ForeignScanState *node)
#define EXEC_FLAG_BACKWARD
Definition: executor.h:60
#define outerPlanState(node)
Definition: execnodes.h:893
EndForeignScan_function EndForeignScan
Definition: fdwapi.h:186
void ExecForeignScanInitializeWorker(ForeignScanState *node, shm_toc *toc)
#define TupIsNull(slot)
Definition: tuptable.h:138
struct FdwRoutine * fdwroutine
Definition: execnodes.h:1548
Oid t_tableOid
Definition: htup.h:66
List * fdw_recheck_quals
Definition: plannodes.h:603
Bitmapset * chgParam
Definition: execnodes.h:875
TupleDesc ExecTypeFromTL(List *targetList, bool hasoid)
Definition: execTuples.c:888
#define outerPlan(node)
Definition: plannodes.h:174
static TupleTableSlot * ForeignNext(ForeignScanState *node)
BeginDirectModify_function BeginDirectModify
Definition: fdwapi.h:209
ExecProcNodeMtd ExecProcNode
Definition: execnodes.h:853
void ExecForeignScanInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
unsigned int Index
Definition: c.h:359
InitializeDSMForeignScan_function InitializeDSMForeignScan
Definition: fdwapi.h:232
Plan * plan
Definition: execnodes.h:847
#define makeNode(_type_)
Definition: nodes.h:558
#define Assert(condition)
Definition: c.h:681
ReScanForeignScan_function ReScanForeignScan
Definition: fdwapi.h:185
#define EXEC_FLAG_MARK
Definition: executor.h:61
IterateForeignScan_function IterateForeignScan
Definition: fdwapi.h:184
void ExecForeignScanEstimate(ForeignScanState *node, ParallelContext *pcxt)
void ExecAssignExprContext(EState *estate, PlanState *planstate)
Definition: execUtils.c:423
#define shm_toc_estimate_keys(e, cnt)
Definition: shm_toc.h:53
void ExecCloseScanRelation(Relation scanrel)
Definition: execUtils.c:666
TupleTableSlot * ecxt_scantuple
Definition: execnodes.h:197
void * shm_toc_allocate(shm_toc *toc, Size nbytes)
Definition: shm_toc.c:88
HeapTuple ExecMaterializeSlot(TupleTableSlot *slot)
Definition: execTuples.c:725
ExprState * qual
Definition: execnodes.h:865
ReInitializeDSMForeignScan_function ReInitializeDSMForeignScan
Definition: fdwapi.h:233
ShutdownForeignScan_function ShutdownForeignScan
Definition: fdwapi.h:235
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:329
void ExecShutdownForeignScan(ForeignScanState *node)
void ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc)
Definition: execUtils.c:545
#define INDEX_VAR
Definition: primnodes.h:155
PlanState * ExecInitNode(Plan *node, EState *estate, int eflags)
Definition: execProcnode.c:139
#define RelationGetRelid(relation)
Definition: rel.h:416
void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError)
Definition: shm_toc.c:232
#define ResetExprContext(econtext)
Definition: executor.h:471
shm_toc * toc
Definition: parallel.h:44
bool fsSystemCol
Definition: plannodes.h:605