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nodeMaterial.c
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1 /*-------------------------------------------------------------------------
2  *
3  * nodeMaterial.c
4  * Routines to handle materialization nodes.
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/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 */
40 {
41  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 
50 
51  /*
52  * get state info from node
53  */
54  estate = node->ss.ps.state;
55  dir = estate->es_direction;
56  forward = ScanDirectionIsForward(dir);
57  tuplestorestate = node->tuplestorestate;
58 
59  /*
60  * If first time through, and we need a tuplestore, initialize it.
61  */
62  if (tuplestorestate == NULL && node->eflags != 0)
63  {
64  tuplestorestate = tuplestore_begin_heap(true, false, work_mem);
65  tuplestore_set_eflags(tuplestorestate, node->eflags);
66  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  ptrno = tuplestore_alloc_read_pointer(tuplestorestate,
75  node->eflags);
76  Assert(ptrno == 1);
77  }
78  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  eof_tuplestore = (tuplestorestate == NULL) ||
86  tuplestore_ateof(tuplestorestate);
87 
88  if (!forward && eof_tuplestore)
89  {
90  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  if (!tuplestore_advance(tuplestorestate, forward))
99  return NULL; /* the tuplestore must be empty */
100  }
101  eof_tuplestore = false;
102  }
103 
104  /*
105  * If we can fetch another tuple from the tuplestore, return it.
106  */
107  slot = node->ss.ps.ps_ResultTupleSlot;
108  if (!eof_tuplestore)
109  {
110  if (tuplestore_gettupleslot(tuplestorestate, forward, false, slot))
111  return slot;
112  if (forward)
113  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  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  outerNode = outerPlanState(node);
134  outerslot = ExecProcNode(outerNode);
135  if (TupIsNull(outerslot))
136  {
137  node->eof_underlying = true;
138  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  if (tuplestorestate)
147  tuplestore_puttupleslot(tuplestorestate, outerslot);
148 
149  /*
150  * We can just return the subplan's returned tuple, without copying.
151  */
152  return outerslot;
153  }
154 
155  /*
156  * Nothing left ...
157  */
158  return ExecClearTuple(slot);
159 }
160 
161 /* ----------------------------------------------------------------
162  * ExecInitMaterial
163  * ----------------------------------------------------------------
164  */
166 ExecInitMaterial(Material *node, EState *estate, int eflags)
167 {
168  MaterialState *matstate;
169  Plan *outerPlan;
170 
171  /*
172  * create state structure
173  */
174  matstate = makeNode(MaterialState);
175  matstate->ss.ps.plan = (Plan *) node;
176  matstate->ss.ps.state = estate;
177  matstate->ss.ps.ExecProcNode = ExecMaterial;
178 
179  /*
180  * We must have a tuplestore buffering the subplan output to do backward
181  * scan or mark/restore. We also prefer to materialize the subplan output
182  * if we might be called on to rewind and replay it many times. However,
183  * if none of these cases apply, we can skip storing the data.
184  */
185  matstate->eflags = (eflags & (EXEC_FLAG_REWIND |
187  EXEC_FLAG_MARK));
188 
189  /*
190  * Tuplestore's interpretation of the flag bits is subtly different from
191  * the general executor meaning: it doesn't think BACKWARD necessarily
192  * means "backwards all the way to start". If told to support BACKWARD we
193  * must include REWIND in the tuplestore eflags, else tuplestore_trim
194  * might throw away too much.
195  */
196  if (eflags & EXEC_FLAG_BACKWARD)
197  matstate->eflags |= EXEC_FLAG_REWIND;
198 
199  matstate->eof_underlying = false;
200  matstate->tuplestorestate = NULL;
201 
202  /*
203  * Miscellaneous initialization
204  *
205  * Materialization nodes don't need ExprContexts because they never call
206  * ExecQual or ExecProject.
207  */
208 
209  /*
210  * tuple table initialization
211  *
212  * material nodes only return tuples from their materialized relation.
213  */
214  ExecInitResultTupleSlot(estate, &matstate->ss.ps);
215  ExecInitScanTupleSlot(estate, &matstate->ss);
216 
217  /*
218  * initialize child nodes
219  *
220  * We shield the child node from the need to support REWIND, BACKWARD, or
221  * MARK/RESTORE.
222  */
223  eflags &= ~(EXEC_FLAG_REWIND | EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK);
224 
225  outerPlan = outerPlan(node);
226  outerPlanState(matstate) = ExecInitNode(outerPlan, estate, eflags);
227 
228  /*
229  * initialize tuple type. no need to initialize projection info because
230  * this node doesn't do projections.
231  */
232  ExecAssignResultTypeFromTL(&matstate->ss.ps);
234  matstate->ss.ps.ps_ProjInfo = NULL;
235 
236  return matstate;
237 }
238 
239 /* ----------------------------------------------------------------
240  * ExecEndMaterial
241  * ----------------------------------------------------------------
242  */
243 void
245 {
246  /*
247  * clean out the tuple table
248  */
250 
251  /*
252  * Release tuplestore resources
253  */
254  if (node->tuplestorestate != NULL)
256  node->tuplestorestate = NULL;
257 
258  /*
259  * shut down the subplan
260  */
262 }
263 
264 /* ----------------------------------------------------------------
265  * ExecMaterialMarkPos
266  *
267  * Calls tuplestore to save the current position in the stored file.
268  * ----------------------------------------------------------------
269  */
270 void
272 {
273  Assert(node->eflags & EXEC_FLAG_MARK);
274 
275  /*
276  * if we haven't materialized yet, just return.
277  */
278  if (!node->tuplestorestate)
279  return;
280 
281  /*
282  * copy the active read pointer to the mark.
283  */
285 
286  /*
287  * since we may have advanced the mark, try to truncate the tuplestore.
288  */
290 }
291 
292 /* ----------------------------------------------------------------
293  * ExecMaterialRestrPos
294  *
295  * Calls tuplestore to restore the last saved file position.
296  * ----------------------------------------------------------------
297  */
298 void
300 {
301  Assert(node->eflags & EXEC_FLAG_MARK);
302 
303  /*
304  * if we haven't materialized yet, just return.
305  */
306  if (!node->tuplestorestate)
307  return;
308 
309  /*
310  * copy the mark to the active read pointer.
311  */
313 }
314 
315 /* ----------------------------------------------------------------
316  * ExecReScanMaterial
317  *
318  * Rescans the materialized relation.
319  * ----------------------------------------------------------------
320  */
321 void
323 {
325 
327 
328  if (node->eflags != 0)
329  {
330  /*
331  * If we haven't materialized yet, just return. If outerplan's
332  * chgParam is not NULL then it will be re-scanned by ExecProcNode,
333  * else no reason to re-scan it at all.
334  */
335  if (!node->tuplestorestate)
336  return;
337 
338  /*
339  * If subnode is to be rescanned then we forget previous stored
340  * results; we have to re-read the subplan and re-store. Also, if we
341  * told tuplestore it needn't support rescan, we lose and must
342  * re-read. (This last should not happen in common cases; else our
343  * caller lied by not passing EXEC_FLAG_REWIND to us.)
344  *
345  * Otherwise we can just rewind and rescan the stored output. The
346  * state of the subnode does not change.
347  */
348  if (outerPlan->chgParam != NULL ||
349  (node->eflags & EXEC_FLAG_REWIND) == 0)
350  {
352  node->tuplestorestate = NULL;
353  if (outerPlan->chgParam == NULL)
354  ExecReScan(outerPlan);
355  node->eof_underlying = false;
356  }
357  else
359  }
360  else
361  {
362  /* In this case we are just passing on the subquery's output */
363 
364  /*
365  * if chgParam of subnode is not null then plan will be re-scanned by
366  * first ExecProcNode.
367  */
368  if (outerPlan->chgParam == NULL)
369  ExecReScan(outerPlan);
370  node->eof_underlying = false;
371  }
372 }
void tuplestore_rescan(Tuplestorestate *state)
Definition: tuplestore.c:1233
void tuplestore_puttupleslot(Tuplestorestate *state, TupleTableSlot *slot)
Definition: tuplestore.c:708
bool tuplestore_advance(Tuplestorestate *state, bool forward)
Definition: tuplestore.c:1110
void ExecMaterialRestrPos(MaterialState *node)
Definition: nodeMaterial.c:299
void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate)
Definition: execTuples.c:842
Tuplestorestate * tuplestorestate
Definition: execnodes.h:1733
ProjectionInfo * ps_ProjInfo
Definition: execnodes.h:882
#define ScanDirectionIsForward(direction)
Definition: sdir.h:55
#define castNode(_type_, nodeptr)
Definition: nodes.h:579
void tuplestore_trim(Tuplestorestate *state)
Definition: tuplestore.c:1360
void ExecEndNode(PlanState *node)
Definition: execProcnode.c:523
void tuplestore_set_eflags(Tuplestorestate *state, int eflags)
Definition: tuplestore.c:359
void ExecReScanMaterial(MaterialState *node)
Definition: nodeMaterial.c:322
void ExecReScan(PlanState *node)
Definition: execAmi.c:76
TupleTableSlot * ExecClearTuple(TupleTableSlot *slot)
Definition: execTuples.c:439
ScanState ss
Definition: execnodes.h:1730
TupleTableSlot * ss_ScanTupleSlot
Definition: execnodes.h:1104
EState * state
Definition: execnodes.h:849
static TupleTableSlot * ExecMaterial(PlanState *pstate)
Definition: nodeMaterial.c:39
ScanDirection es_direction
Definition: execnodes.h:428
void ExecAssignResultTypeFromTL(PlanState *planstate)
Definition: execUtils.c:445
PlanState ps
Definition: execnodes.h:1101
TupleTableSlot * ps_ResultTupleSlot
Definition: execnodes.h:880
void ExecInitResultTupleSlot(EState *estate, PlanState *planstate)
Definition: execTuples.c:832
#define EXEC_FLAG_BACKWARD
Definition: executor.h:60
#define outerPlanState(node)
Definition: execnodes.h:893
ScanDirection
Definition: sdir.h:22
#define TupIsNull(slot)
Definition: tuptable.h:138
bool eof_underlying
Definition: execnodes.h:1732
void tuplestore_copy_read_pointer(Tuplestorestate *state, int srcptr, int destptr)
Definition: tuplestore.c:1268
#define EXEC_FLAG_REWIND
Definition: executor.h:59
Bitmapset * chgParam
Definition: execnodes.h:875
#define outerPlan(node)
Definition: plannodes.h:174
Tuplestorestate * tuplestore_begin_heap(bool randomAccess, bool interXact, int maxKBytes)
Definition: tuplestore.c:318
ExecProcNodeMtd ExecProcNode
Definition: execnodes.h:853
static TupleTableSlot * ExecProcNode(PlanState *node)
Definition: executor.h:246
int work_mem
Definition: globals.c:113
Plan * plan
Definition: execnodes.h:847
#define makeNode(_type_)
Definition: nodes.h:558
bool tuplestore_gettupleslot(Tuplestorestate *state, bool forward, bool copy, TupleTableSlot *slot)
Definition: tuplestore.c:1078
#define Assert(condition)
Definition: c.h:681
#define EXEC_FLAG_MARK
Definition: executor.h:61
void tuplestore_end(Tuplestorestate *state)
Definition: tuplestore.c:453
int tuplestore_alloc_read_pointer(Tuplestorestate *state, int eflags)
Definition: tuplestore.c:383
void ExecAssignScanTypeFromOuterPlan(ScanState *scanstate)
Definition: execUtils.c:557
void ExecMaterialMarkPos(MaterialState *node)
Definition: nodeMaterial.c:271
void ExecEndMaterial(MaterialState *node)
Definition: nodeMaterial.c:244
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:98
bool tuplestore_ateof(Tuplestorestate *state)
Definition: tuplestore.c:557
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:996
PlanState * ExecInitNode(Plan *node, EState *estate, int eflags)
Definition: execProcnode.c:139
MaterialState * ExecInitMaterial(Material *node, EState *estate, int eflags)
Definition: nodeMaterial.c:166