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"
26 #include "executor/nodeForeignscan.h"
27 #include "foreign/fdwapi.h"
28 #include "utils/memutils.h"
29 #include "utils/rel.h"
30
31 static TupleTableSlot *ForeignNext(ForeignScanState *node);
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 *
ForeignNext(ForeignScanState * node)42 ForeignNext(ForeignScanState *node)
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
67 tup->t_tableOid = RelationGetRelid(node->ss.ss_currentRelation);
68 }
69
70 return slot;
71 }
72
73 /*
74 * ForeignRecheck -- access method routine to recheck a tuple in EvalPlanQual
75 */
76 static bool
ForeignRecheck(ForeignScanState * node,TupleTableSlot * slot)77 ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot)
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 *
ExecForeignScan(PlanState * pstate)117 ExecForeignScan(PlanState *pstate)
118 {
119 ForeignScanState *node = castNode(ForeignScanState, pstate);
120
121 return ExecScan(&node->ss,
122 (ExecScanAccessMtd) ForeignNext,
123 (ExecScanRecheckMtd) ForeignRecheck);
124 }
125
126
127 /* ----------------------------------------------------------------
128 * ExecInitForeignScan
129 * ----------------------------------------------------------------
130 */
131 ForeignScanState *
ExecInitForeignScan(ForeignScan * node,EState * estate,int eflags)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
ExecEndForeignScan(ForeignScanState * node)243 ExecEndForeignScan(ForeignScanState *node)
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))
255 ExecEndNode(outerPlanState(node));
256
257 /* Free the exprcontext */
258 ExecFreeExprContext(&node->ss.ps);
259
260 /* clean out the tuple table */
261 ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
262 ExecClearTuple(node->ss.ss_ScanTupleSlot);
263
264 /* close the relation. */
265 if (node->ss.ss_currentRelation)
266 ExecCloseScanRelation(node->ss.ss_currentRelation);
267 }
268
269 /* ----------------------------------------------------------------
270 * ExecReScanForeignScan
271 *
272 * Rescans the relation.
273 * ----------------------------------------------------------------
274 */
275 void
ExecReScanForeignScan(ForeignScanState * node)276 ExecReScanForeignScan(ForeignScanState *node)
277 {
278 PlanState *outerPlan = outerPlanState(node);
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
ExecForeignScanEstimate(ForeignScanState * node,ParallelContext * pcxt)300 ExecForeignScanEstimate(ForeignScanState *node, ParallelContext *pcxt)
301 {
302 FdwRoutine *fdwroutine = node->fdwroutine;
303
304 if (fdwroutine->EstimateDSMForeignScan)
305 {
306 node->pscan_len = fdwroutine->EstimateDSMForeignScan(node, pcxt);
307 shm_toc_estimate_chunk(&pcxt->estimator, node->pscan_len);
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
ExecForeignScanInitializeDSM(ForeignScanState * node,ParallelContext * pcxt)319 ExecForeignScanInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
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
ExecForeignScanReInitializeDSM(ForeignScanState * node,ParallelContext * pcxt)341 ExecForeignScanReInitializeDSM(ForeignScanState *node, ParallelContext *pcxt)
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
ExecForeignScanInitializeWorker(ForeignScanState * node,shm_toc * toc)362 ExecForeignScanInitializeWorker(ForeignScanState *node, shm_toc *toc)
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
ExecShutdownForeignScan(ForeignScanState * node)384 ExecShutdownForeignScan(ForeignScanState *node)
385 {
386 FdwRoutine *fdwroutine = node->fdwroutine;
387
388 if (fdwroutine->ShutdownForeignScan)
389 fdwroutine->ShutdownForeignScan(node);
390 }
391