Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * nodeMaterial.c
4 : * Routines to handle materialization nodes.
5 : *
6 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/executor/nodeMaterial.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : /*
16 : * INTERFACE ROUTINES
17 : * ExecMaterial - materialize the result of a subplan
18 : * ExecInitMaterial - initialize node and subnodes
19 : * ExecEndMaterial - shutdown node and subnodes
20 : *
21 : */
22 : #include "postgres.h"
23 :
24 : #include "executor/executor.h"
25 : #include "executor/nodeMaterial.h"
26 : #include "miscadmin.h"
27 :
28 : /* ----------------------------------------------------------------
29 : * ExecMaterial
30 : *
31 : * As long as we are at the end of the data collected in the tuplestore,
32 : * we collect one new row from the subplan on each call, and stash it
33 : * aside in the tuplestore before returning it. The tuplestore is
34 : * only read if we are asked to scan backwards, rescan, or mark/restore.
35 : *
36 : * ----------------------------------------------------------------
37 : */
38 : static TupleTableSlot * /* result tuple from subplan */
39 2134926 : ExecMaterial(PlanState *pstate)
40 : {
41 2134926 : MaterialState *node = castNode(MaterialState, pstate);
42 : EState *estate;
43 : ScanDirection dir;
44 : bool forward;
45 : Tuplestorestate *tuplestorestate;
46 : bool eof_tuplestore;
47 : TupleTableSlot *slot;
48 :
49 2134926 : CHECK_FOR_INTERRUPTS();
50 :
51 : /*
52 : * get state info from node
53 : */
54 2134926 : estate = node->ss.ps.state;
55 2134926 : dir = estate->es_direction;
56 2134926 : forward = ScanDirectionIsForward(dir);
57 2134926 : tuplestorestate = node->tuplestorestate;
58 :
59 : /*
60 : * If first time through, and we need a tuplestore, initialize it.
61 : */
62 2134926 : if (tuplestorestate == NULL && node->eflags != 0)
63 : {
64 2884 : tuplestorestate = tuplestore_begin_heap(true, false, work_mem);
65 2884 : tuplestore_set_eflags(tuplestorestate, node->eflags);
66 2884 : if (node->eflags & EXEC_FLAG_MARK)
67 : {
68 : /*
69 : * Allocate a second read pointer to serve as the mark. We know it
70 : * must have index 1, so needn't store that.
71 : */
72 : int ptrno PG_USED_FOR_ASSERTS_ONLY;
73 :
74 120 : ptrno = tuplestore_alloc_read_pointer(tuplestorestate,
75 : node->eflags);
76 : Assert(ptrno == 1);
77 : }
78 2884 : node->tuplestorestate = tuplestorestate;
79 : }
80 :
81 : /*
82 : * If we are not at the end of the tuplestore, or are going backwards, try
83 : * to fetch a tuple from tuplestore.
84 : */
85 4269722 : eof_tuplestore = (tuplestorestate == NULL) ||
86 2134796 : tuplestore_ateof(tuplestorestate);
87 :
88 2134926 : if (!forward && eof_tuplestore)
89 : {
90 12 : if (!node->eof_underlying)
91 : {
92 : /*
93 : * When reversing direction at tuplestore EOF, the first
94 : * gettupleslot call will fetch the last-added tuple; but we want
95 : * to return the one before that, if possible. So do an extra
96 : * fetch.
97 : */
98 0 : if (!tuplestore_advance(tuplestorestate, forward))
99 0 : return NULL; /* the tuplestore must be empty */
100 : }
101 12 : eof_tuplestore = false;
102 : }
103 :
104 : /*
105 : * If we can fetch another tuple from the tuplestore, return it.
106 : */
107 2134926 : slot = node->ss.ps.ps_ResultTupleSlot;
108 2134926 : if (!eof_tuplestore)
109 : {
110 2108974 : if (tuplestore_gettupleslot(tuplestorestate, forward, false, slot))
111 1977184 : return slot;
112 131790 : if (forward)
113 131778 : eof_tuplestore = true;
114 : }
115 :
116 : /*
117 : * If necessary, try to fetch another row from the subplan.
118 : *
119 : * Note: the eof_underlying state variable exists to short-circuit further
120 : * subplan calls. It's not optional, unfortunately, because some plan
121 : * node types are not robust about being called again when they've already
122 : * returned NULL.
123 : */
124 157742 : if (eof_tuplestore && !node->eof_underlying)
125 : {
126 : PlanState *outerNode;
127 : TupleTableSlot *outerslot;
128 :
129 : /*
130 : * We can only get here with forward==true, so no need to worry about
131 : * which direction the subplan will go.
132 : */
133 35122 : outerNode = outerPlanState(node);
134 35122 : outerslot = ExecProcNode(outerNode);
135 35122 : if (TupIsNull(outerslot))
136 : {
137 2700 : node->eof_underlying = true;
138 2700 : return NULL;
139 : }
140 :
141 : /*
142 : * Append a copy of the returned tuple to tuplestore. NOTE: because
143 : * the tuplestore is certainly in EOF state, its read position will
144 : * move forward over the added tuple. This is what we want.
145 : */
146 32422 : if (tuplestorestate)
147 32298 : tuplestore_puttupleslot(tuplestorestate, outerslot);
148 :
149 32422 : ExecCopySlot(slot, outerslot);
150 32422 : return slot;
151 : }
152 :
153 : /*
154 : * Nothing left ...
155 : */
156 122620 : return ExecClearTuple(slot);
157 : }
158 :
159 : /* ----------------------------------------------------------------
160 : * ExecInitMaterial
161 : * ----------------------------------------------------------------
162 : */
163 : MaterialState *
164 4018 : ExecInitMaterial(Material *node, EState *estate, int eflags)
165 : {
166 : MaterialState *matstate;
167 : Plan *outerPlan;
168 :
169 : /*
170 : * create state structure
171 : */
172 4018 : matstate = makeNode(MaterialState);
173 4018 : matstate->ss.ps.plan = (Plan *) node;
174 4018 : matstate->ss.ps.state = estate;
175 4018 : matstate->ss.ps.ExecProcNode = ExecMaterial;
176 :
177 : /*
178 : * We must have a tuplestore buffering the subplan output to do backward
179 : * scan or mark/restore. We also prefer to materialize the subplan output
180 : * if we might be called on to rewind and replay it many times. However,
181 : * if none of these cases apply, we can skip storing the data.
182 : */
183 4018 : matstate->eflags = (eflags & (EXEC_FLAG_REWIND |
184 : EXEC_FLAG_BACKWARD |
185 : EXEC_FLAG_MARK));
186 :
187 : /*
188 : * Tuplestore's interpretation of the flag bits is subtly different from
189 : * the general executor meaning: it doesn't think BACKWARD necessarily
190 : * means "backwards all the way to start". If told to support BACKWARD we
191 : * must include REWIND in the tuplestore eflags, else tuplestore_trim
192 : * might throw away too much.
193 : */
194 4018 : if (eflags & EXEC_FLAG_BACKWARD)
195 18 : matstate->eflags |= EXEC_FLAG_REWIND;
196 :
197 4018 : matstate->eof_underlying = false;
198 4018 : matstate->tuplestorestate = NULL;
199 :
200 : /*
201 : * Miscellaneous initialization
202 : *
203 : * Materialization nodes don't need ExprContexts because they never call
204 : * ExecQual or ExecProject.
205 : */
206 :
207 : /*
208 : * initialize child nodes
209 : *
210 : * We shield the child node from the need to support REWIND, BACKWARD, or
211 : * MARK/RESTORE.
212 : */
213 4018 : eflags &= ~(EXEC_FLAG_REWIND | EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK);
214 :
215 4018 : outerPlan = outerPlan(node);
216 4018 : outerPlanState(matstate) = ExecInitNode(outerPlan, estate, eflags);
217 :
218 : /*
219 : * Initialize result type and slot. No need to initialize projection info
220 : * because this node doesn't do projections.
221 : *
222 : * material nodes only return tuples from their materialized relation.
223 : */
224 4018 : ExecInitResultTupleSlotTL(&matstate->ss.ps, &TTSOpsMinimalTuple);
225 4018 : matstate->ss.ps.ps_ProjInfo = NULL;
226 :
227 : /*
228 : * initialize tuple type.
229 : */
230 4018 : ExecCreateScanSlotFromOuterPlan(estate, &matstate->ss, &TTSOpsMinimalTuple);
231 :
232 4018 : return matstate;
233 : }
234 :
235 : /* ----------------------------------------------------------------
236 : * ExecEndMaterial
237 : * ----------------------------------------------------------------
238 : */
239 : void
240 3958 : ExecEndMaterial(MaterialState *node)
241 : {
242 : /*
243 : * Release tuplestore resources
244 : */
245 3958 : if (node->tuplestorestate != NULL)
246 2812 : tuplestore_end(node->tuplestorestate);
247 3958 : node->tuplestorestate = NULL;
248 :
249 : /*
250 : * shut down the subplan
251 : */
252 3958 : ExecEndNode(outerPlanState(node));
253 3958 : }
254 :
255 : /* ----------------------------------------------------------------
256 : * ExecMaterialMarkPos
257 : *
258 : * Calls tuplestore to save the current position in the stored file.
259 : * ----------------------------------------------------------------
260 : */
261 : void
262 6638 : ExecMaterialMarkPos(MaterialState *node)
263 : {
264 : Assert(node->eflags & EXEC_FLAG_MARK);
265 :
266 : /*
267 : * if we haven't materialized yet, just return.
268 : */
269 6638 : if (!node->tuplestorestate)
270 12 : return;
271 :
272 : /*
273 : * copy the active read pointer to the mark.
274 : */
275 6626 : tuplestore_copy_read_pointer(node->tuplestorestate, 0, 1);
276 :
277 : /*
278 : * since we may have advanced the mark, try to truncate the tuplestore.
279 : */
280 6626 : tuplestore_trim(node->tuplestorestate);
281 : }
282 :
283 : /* ----------------------------------------------------------------
284 : * ExecMaterialRestrPos
285 : *
286 : * Calls tuplestore to restore the last saved file position.
287 : * ----------------------------------------------------------------
288 : */
289 : void
290 54306 : ExecMaterialRestrPos(MaterialState *node)
291 : {
292 : Assert(node->eflags & EXEC_FLAG_MARK);
293 :
294 : /*
295 : * if we haven't materialized yet, just return.
296 : */
297 54306 : if (!node->tuplestorestate)
298 0 : return;
299 :
300 : /*
301 : * copy the mark to the active read pointer.
302 : */
303 54306 : tuplestore_copy_read_pointer(node->tuplestorestate, 1, 0);
304 : }
305 :
306 : /* ----------------------------------------------------------------
307 : * ExecReScanMaterial
308 : *
309 : * Rescans the materialized relation.
310 : * ----------------------------------------------------------------
311 : */
312 : void
313 132344 : ExecReScanMaterial(MaterialState *node)
314 : {
315 132344 : PlanState *outerPlan = outerPlanState(node);
316 :
317 132344 : ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
318 :
319 132344 : if (node->eflags != 0)
320 : {
321 : /*
322 : * If we haven't materialized yet, just return. If outerplan's
323 : * chgParam is not NULL then it will be re-scanned by ExecProcNode,
324 : * else no reason to re-scan it at all.
325 : */
326 132340 : if (!node->tuplestorestate)
327 2746 : return;
328 :
329 : /*
330 : * If subnode is to be rescanned then we forget previous stored
331 : * results; we have to re-read the subplan and re-store. Also, if we
332 : * told tuplestore it needn't support rescan, we lose and must
333 : * re-read. (This last should not happen in common cases; else our
334 : * caller lied by not passing EXEC_FLAG_REWIND to us.)
335 : *
336 : * Otherwise we can just rewind and rescan the stored output. The
337 : * state of the subnode does not change.
338 : */
339 129594 : if (outerPlan->chgParam != NULL ||
340 129582 : (node->eflags & EXEC_FLAG_REWIND) == 0)
341 : {
342 12 : tuplestore_end(node->tuplestorestate);
343 12 : node->tuplestorestate = NULL;
344 12 : if (outerPlan->chgParam == NULL)
345 0 : ExecReScan(outerPlan);
346 12 : node->eof_underlying = false;
347 : }
348 : else
349 129582 : tuplestore_rescan(node->tuplestorestate);
350 : }
351 : else
352 : {
353 : /* In this case we are just passing on the subquery's output */
354 :
355 : /*
356 : * if chgParam of subnode is not null then plan will be re-scanned by
357 : * first ExecProcNode.
358 : */
359 4 : if (outerPlan->chgParam == NULL)
360 0 : ExecReScan(outerPlan);
361 4 : node->eof_underlying = false;
362 : }
363 : }
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