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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) 1996-2019, 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  * Insert valid value into tableoid, the only actually-useful system
59  * column.
60  */
61  if (plan->fsSystemCol && !TupIsNull(slot))
63 
64  return slot;
65 }
66 
67 /*
68  * ForeignRecheck -- access method routine to recheck a tuple in EvalPlanQual
69  */
70 static bool
72 {
73  FdwRoutine *fdwroutine = node->fdwroutine;
74  ExprContext *econtext;
75 
76  /*
77  * extract necessary information from foreign scan node
78  */
79  econtext = node->ss.ps.ps_ExprContext;
80 
81  /* Does the tuple meet the remote qual condition? */
82  econtext->ecxt_scantuple = slot;
83 
84  ResetExprContext(econtext);
85 
86  /*
87  * If an outer join is pushed down, RecheckForeignScan may need to store a
88  * different tuple in the slot, because a different set of columns may go
89  * to NULL upon recheck. Otherwise, it shouldn't need to change the slot
90  * contents, just return true or false to indicate whether the quals still
91  * pass. For simple cases, setting fdw_recheck_quals may be easier than
92  * providing this callback.
93  */
94  if (fdwroutine->RecheckForeignScan &&
95  !fdwroutine->RecheckForeignScan(node, slot))
96  return false;
97 
98  return ExecQual(node->fdw_recheck_quals, econtext);
99 }
100 
101 /* ----------------------------------------------------------------
102  * ExecForeignScan(node)
103  *
104  * Fetches the next tuple from the FDW, checks local quals, and
105  * returns it.
106  * We call the ExecScan() routine and pass it the appropriate
107  * access method functions.
108  * ----------------------------------------------------------------
109  */
110 static TupleTableSlot *
112 {
113  ForeignScanState *node = castNode(ForeignScanState, pstate);
114 
115  return ExecScan(&node->ss,
118 }
119 
120 
121 /* ----------------------------------------------------------------
122  * ExecInitForeignScan
123  * ----------------------------------------------------------------
124  */
126 ExecInitForeignScan(ForeignScan *node, EState *estate, int eflags)
127 {
128  ForeignScanState *scanstate;
129  Relation currentRelation = NULL;
130  Index scanrelid = node->scan.scanrelid;
131  Index tlistvarno;
132  FdwRoutine *fdwroutine;
133 
134  /* check for unsupported flags */
135  Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
136 
137  /*
138  * create state structure
139  */
140  scanstate = makeNode(ForeignScanState);
141  scanstate->ss.ps.plan = (Plan *) node;
142  scanstate->ss.ps.state = estate;
143  scanstate->ss.ps.ExecProcNode = ExecForeignScan;
144 
145  /*
146  * Miscellaneous initialization
147  *
148  * create expression context for node
149  */
150  ExecAssignExprContext(estate, &scanstate->ss.ps);
151 
152  /*
153  * open the scan relation, if any; also acquire function pointers from the
154  * FDW's handler
155  */
156  if (scanrelid > 0)
157  {
158  currentRelation = ExecOpenScanRelation(estate, scanrelid, eflags);
159  scanstate->ss.ss_currentRelation = currentRelation;
160  fdwroutine = GetFdwRoutineForRelation(currentRelation, true);
161  }
162  else
163  {
164  /* We can't use the relcache, so get fdwroutine the hard way */
165  fdwroutine = GetFdwRoutineByServerId(node->fs_server);
166  }
167 
168  /*
169  * Determine the scan tuple type. If the FDW provided a targetlist
170  * describing the scan tuples, use that; else use base relation's rowtype.
171  */
172  if (node->fdw_scan_tlist != NIL || currentRelation == NULL)
173  {
174  TupleDesc scan_tupdesc;
175 
176  scan_tupdesc = ExecTypeFromTL(node->fdw_scan_tlist);
177  ExecInitScanTupleSlot(estate, &scanstate->ss, scan_tupdesc,
178  &TTSOpsHeapTuple);
179  /* Node's targetlist will contain Vars with varno = INDEX_VAR */
180  tlistvarno = INDEX_VAR;
181  }
182  else
183  {
184  TupleDesc scan_tupdesc;
185 
186  /* don't trust FDWs to return tuples fulfilling NOT NULL constraints */
187  scan_tupdesc = CreateTupleDescCopy(RelationGetDescr(currentRelation));
188  ExecInitScanTupleSlot(estate, &scanstate->ss, scan_tupdesc,
189  &TTSOpsHeapTuple);
190  /* Node's targetlist will contain Vars with varno = scanrelid */
191  tlistvarno = scanrelid;
192  }
193 
194  /* Don't know what an FDW might return */
195  scanstate->ss.ps.scanopsfixed = false;
196  scanstate->ss.ps.scanopsset = true;
197 
198  /*
199  * Initialize result slot, type and projection.
200  */
201  ExecInitResultTypeTL(&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 */
259  if (node->ss.ps.ps_ResultTupleSlot)
262 }
263 
264 /* ----------------------------------------------------------------
265  * ExecReScanForeignScan
266  *
267  * Rescans the relation.
268  * ----------------------------------------------------------------
269  */
270 void
272 {
274 
275  node->fdwroutine->ReScanForeignScan(node);
276 
277  /*
278  * If chgParam of subnode is not null then plan will be re-scanned by
279  * first ExecProcNode. outerPlan may also be NULL, in which case there is
280  * nothing to rescan at all.
281  */
282  if (outerPlan != NULL && outerPlan->chgParam == NULL)
283  ExecReScan(outerPlan);
284 
285  ExecScanReScan(&node->ss);
286 }
287 
288 /* ----------------------------------------------------------------
289  * ExecForeignScanEstimate
290  *
291  * Informs size of the parallel coordination information, if any
292  * ----------------------------------------------------------------
293  */
294 void
296 {
297  FdwRoutine *fdwroutine = node->fdwroutine;
298 
299  if (fdwroutine->EstimateDSMForeignScan)
300  {
301  node->pscan_len = fdwroutine->EstimateDSMForeignScan(node, pcxt);
303  shm_toc_estimate_keys(&pcxt->estimator, 1);
304  }
305 }
306 
307 /* ----------------------------------------------------------------
308  * ExecForeignScanInitializeDSM
309  *
310  * Initialize the parallel coordination information
311  * ----------------------------------------------------------------
312  */
313 void
315 {
316  FdwRoutine *fdwroutine = node->fdwroutine;
317 
318  if (fdwroutine->InitializeDSMForeignScan)
319  {
320  int plan_node_id = node->ss.ps.plan->plan_node_id;
321  void *coordinate;
322 
323  coordinate = shm_toc_allocate(pcxt->toc, node->pscan_len);
324  fdwroutine->InitializeDSMForeignScan(node, pcxt, coordinate);
325  shm_toc_insert(pcxt->toc, plan_node_id, coordinate);
326  }
327 }
328 
329 /* ----------------------------------------------------------------
330  * ExecForeignScanReInitializeDSM
331  *
332  * Reset shared state before beginning a fresh scan.
333  * ----------------------------------------------------------------
334  */
335 void
337 {
338  FdwRoutine *fdwroutine = node->fdwroutine;
339 
340  if (fdwroutine->ReInitializeDSMForeignScan)
341  {
342  int plan_node_id = node->ss.ps.plan->plan_node_id;
343  void *coordinate;
344 
345  coordinate = shm_toc_lookup(pcxt->toc, plan_node_id, false);
346  fdwroutine->ReInitializeDSMForeignScan(node, pcxt, coordinate);
347  }
348 }
349 
350 /* ----------------------------------------------------------------
351  * ExecForeignScanInitializeWorker
352  *
353  * Initialization according to the parallel coordination information
354  * ----------------------------------------------------------------
355  */
356 void
358  ParallelWorkerContext *pwcxt)
359 {
360  FdwRoutine *fdwroutine = node->fdwroutine;
361 
362  if (fdwroutine->InitializeWorkerForeignScan)
363  {
364  int plan_node_id = node->ss.ps.plan->plan_node_id;
365  void *coordinate;
366 
367  coordinate = shm_toc_lookup(pwcxt->toc, plan_node_id, false);
368  fdwroutine->InitializeWorkerForeignScan(node, pwcxt->toc, coordinate);
369  }
370 }
371 
372 /* ----------------------------------------------------------------
373  * ExecShutdownForeignScan
374  *
375  * Gives FDW chance to stop asynchronous resource consumption
376  * and release any resources still held.
377  * ----------------------------------------------------------------
378  */
379 void
381 {
382  FdwRoutine *fdwroutine = node->fdwroutine;
383 
384  if (fdwroutine->ShutdownForeignScan)
385  fdwroutine->ShutdownForeignScan(node);
386 }
void ExecForeignScanInitializeWorker(ForeignScanState *node, ParallelWorkerContext *pwcxt)
BeginForeignScan_function BeginForeignScan
Definition: fdwapi.h:191
EndDirectModify_function EndDirectModify
Definition: fdwapi.h:221
#define NIL
Definition: pg_list.h:65
Oid tts_tableOid
Definition: tuptable.h:131
ScanState ss
Definition: execnodes.h:1785
List * qual
Definition: plannodes.h:141
TupleDesc CreateTupleDescCopy(TupleDesc tupdesc)
Definition: tupdesc.c:110
Plan plan
Definition: plannodes.h:340
EstimateDSMForeignScan_function EstimateDSMForeignScan
Definition: fdwapi.h:241
Index scanrelid
Definition: plannodes.h:341
Oid fs_server
Definition: plannodes.h:612
static TupleTableSlot * ExecClearTuple(TupleTableSlot *slot)
Definition: tuptable.h:426
#define RelationGetDescr(relation)
Definition: rel.h:445
#define castNode(_type_, nodeptr)
Definition: nodes.h:594
void ExecEndNode(PlanState *node)
Definition: execProcnode.c:538
InitializeWorkerForeignScan_function InitializeWorkerForeignScan
Definition: fdwapi.h:244
TupleTableSlot * ExecScan(ScanState *node, ExecScanAccessMtd accessMtd, ExecScanRecheckMtd recheckMtd)
Definition: execScan.c:158
ExprContext * ps_ExprContext
Definition: execnodes.h:979
shm_toc_estimator estimator
Definition: parallel.h:41
void ExecReScan(PlanState *node)
Definition: execAmi.c:77
int plan_node_id
Definition: plannodes.h:139
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
Definition: palloc.h:109
static bool ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot)
FdwRoutine * GetFdwRoutineByServerId(Oid serverid)
Definition: foreign.c:362
static TupleTableSlot * ExecForeignScan(PlanState *pstate)
TupleTableSlot * ss_ScanTupleSlot
Definition: execnodes.h:1334
List * fdw_scan_tlist
Definition: plannodes.h:615
Relation ss_currentRelation
Definition: execnodes.h:1332
EState * state
Definition: execnodes.h:942
ExprState * fdw_recheck_quals
Definition: execnodes.h:1786
static bool ExecQual(ExprState *state, ExprContext *econtext)
Definition: executor.h:365
#define shm_toc_estimate_chunk(e, sz)
Definition: shm_toc.h:51
void ExecFreeExprContext(PlanState *planstate)
Definition: execUtils.c:614
CmdType operation
Definition: plannodes.h:611
ExprState * ExecInitQual(List *qual, PlanState *parent)
Definition: execExpr.c:207
void ExecReScanForeignScan(ForeignScanState *node)
void ExecForeignScanReInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
RecheckForeignScan_function RecheckForeignScan
Definition: fdwapi.h:226
IterateDirectModify_function IterateDirectModify
Definition: fdwapi.h:220
void ExecAssignScanProjectionInfoWithVarno(ScanState *node, Index varno)
Definition: execScan.c:285
PlanState ps
Definition: execnodes.h:1331
TupleTableSlot * ps_ResultTupleSlot
Definition: execnodes.h:978
Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags)
Definition: execUtils.c:693
void ExecEndForeignScan(ForeignScanState *node)
#define EXEC_FLAG_BACKWARD
Definition: executor.h:58
#define outerPlanState(node)
Definition: execnodes.h:1034
void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate, TupleDesc tupledesc, const TupleTableSlotOps *tts_ops)
Definition: execTuples.c:1776
void ExecInitResultTypeTL(PlanState *planstate)
Definition: execTuples.c:1720
EndForeignScan_function EndForeignScan
Definition: fdwapi.h:194
#define TupIsNull(slot)
Definition: tuptable.h:293
struct FdwRoutine * fdwroutine
Definition: execnodes.h:1789
List * fdw_recheck_quals
Definition: plannodes.h:616
Bitmapset * chgParam
Definition: execnodes.h:972
#define outerPlan(node)
Definition: plannodes.h:170
bool(* ExecScanRecheckMtd)(ScanState *node, TupleTableSlot *slot)
Definition: executor.h:426
static TupleTableSlot * ForeignNext(ForeignScanState *node)
BeginDirectModify_function BeginDirectModify
Definition: fdwapi.h:219
ExecProcNodeMtd ExecProcNode
Definition: execnodes.h:946
void ExecForeignScanInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
unsigned int Index
Definition: c.h:475
InitializeDSMForeignScan_function InitializeDSMForeignScan
Definition: fdwapi.h:242
Plan * plan
Definition: execnodes.h:940
bool scanopsfixed
Definition: execnodes.h:1016
#define makeNode(_type_)
Definition: nodes.h:573
#define Assert(condition)
Definition: c.h:732
ReScanForeignScan_function ReScanForeignScan
Definition: fdwapi.h:193
#define EXEC_FLAG_MARK
Definition: executor.h:59
IterateForeignScan_function IterateForeignScan
Definition: fdwapi.h:192
void ExecForeignScanEstimate(ForeignScanState *node, ParallelContext *pcxt)
void ExecAssignExprContext(EState *estate, PlanState *planstate)
Definition: execUtils.c:444
#define shm_toc_estimate_keys(e, cnt)
Definition: shm_toc.h:53
TupleDesc ExecTypeFromTL(List *targetList)
Definition: execTuples.c:1904
TupleTableSlot * ecxt_scantuple
Definition: execnodes.h:224
bool scanopsset
Definition: execnodes.h:1020
void * shm_toc_allocate(shm_toc *toc, Size nbytes)
Definition: shm_toc.c:88
ExprState * qual
Definition: execnodes.h:961
ReInitializeDSMForeignScan_function ReInitializeDSMForeignScan
Definition: fdwapi.h:243
ShutdownForeignScan_function ShutdownForeignScan
Definition: fdwapi.h:245
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:427
const TupleTableSlotOps TTSOpsHeapTuple
Definition: execTuples.c:85
void ExecScanReScan(ScanState *node)
Definition: execScan.c:299
void ExecShutdownForeignScan(ForeignScanState *node)
TupleTableSlot *(* ExecScanAccessMtd)(ScanState *node)
Definition: executor.h:425
#define INDEX_VAR
Definition: primnodes.h:159
PlanState * ExecInitNode(Plan *node, EState *estate, int eflags)
Definition: execProcnode.c:139
#define RelationGetRelid(relation)
Definition: rel.h:419
void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError)
Definition: shm_toc.c:232
#define ResetExprContext(econtext)
Definition: executor.h:495
shm_toc * toc
Definition: parallel.h:44
bool fsSystemCol
Definition: plannodes.h:618