PostgreSQL Source Code  git master
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros
nodeSamplescan.c File Reference
#include "postgres.h"
#include "access/hash.h"
#include "access/relscan.h"
#include "access/tsmapi.h"
#include "executor/executor.h"
#include "executor/nodeSamplescan.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/predicate.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#include "utils/tqual.h"
Include dependency graph for nodeSamplescan.c:

Go to the source code of this file.

Functions

static void InitScanRelation (SampleScanState *node, EState *estate, int eflags)
 
static TupleTableSlotSampleNext (SampleScanState *node)
 
static void tablesample_init (SampleScanState *scanstate)
 
static HeapTuple tablesample_getnext (SampleScanState *scanstate)
 
static bool SampleTupleVisible (HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
 
static bool SampleRecheck (SampleScanState *node, TupleTableSlot *slot)
 
TupleTableSlotExecSampleScan (SampleScanState *node)
 
SampleScanStateExecInitSampleScan (SampleScan *node, EState *estate, int eflags)
 
void ExecEndSampleScan (SampleScanState *node)
 
void ExecReScanSampleScan (SampleScanState *node)
 

Function Documentation

void ExecEndSampleScan ( SampleScanState node)

Definition at line 221 of file nodeSamplescan.c.

References TsmRoutine::EndSampleScan, ExecClearTuple(), ExecCloseScanRelation(), ExecFreeExprContext(), heap_endscan(), ScanState::ps, PlanState::ps_ResultTupleSlot, SampleScanState::ss, ScanState::ss_currentRelation, ScanState::ss_currentScanDesc, ScanState::ss_ScanTupleSlot, and SampleScanState::tsmroutine.

Referenced by ExecEndNode().

222 {
223  /*
224  * Tell sampling function that we finished the scan.
225  */
226  if (node->tsmroutine->EndSampleScan)
227  node->tsmroutine->EndSampleScan(node);
228 
229  /*
230  * Free the exprcontext
231  */
232  ExecFreeExprContext(&node->ss.ps);
233 
234  /*
235  * clean out the tuple table
236  */
239 
240  /*
241  * close heap scan
242  */
243  if (node->ss.ss_currentScanDesc)
245 
246  /*
247  * close the heap relation.
248  */
250 }
void heap_endscan(HeapScanDesc scan)
Definition: heapam.c:1578
TupleTableSlot * ExecClearTuple(TupleTableSlot *slot)
Definition: execTuples.c:439
TupleTableSlot * ss_ScanTupleSlot
Definition: execnodes.h:1061
Relation ss_currentRelation
Definition: execnodes.h:1059
void ExecFreeExprContext(PlanState *planstate)
Definition: execUtils.c:516
PlanState ps
Definition: execnodes.h:1058
TupleTableSlot * ps_ResultTupleSlot
Definition: execnodes.h:842
void ExecCloseScanRelation(Relation scanrel)
Definition: execUtils.c:661
struct TsmRoutine * tsmroutine
Definition: execnodes.h:1084
HeapScanDesc ss_currentScanDesc
Definition: execnodes.h:1060
EndSampleScan_function EndSampleScan
Definition: tsmapi.h:74
ScanState ss
Definition: execnodes.h:1080
SampleScanState* ExecInitSampleScan ( SampleScan node,
EState estate,
int  eflags 
)

Definition at line 141 of file nodeSamplescan.c.

References TableSampleClause::args, SampleScanState::args, Assert, SampleScanState::begun, ExecAssignExprContext(), ExecAssignResultTypeFromTL(), ExecAssignScanProjectionInfo(), ExecInitExpr(), ExecInitExprList(), ExecInitQual(), ExecInitResultTupleSlot(), ExecInitScanTupleSlot(), GetTsmRoutine(), TsmRoutine::InitSampleScan, InitScanRelation(), innerPlan, makeNode, NULL, outerPlan, Scan::plan, PlanState::plan, ScanState::ps, Plan::qual, PlanState::qual, random(), TableSampleClause::repeatable, SampleScanState::repeatable, SampleScan::scan, SampleScanState::seed, SampleScanState::ss, PlanState::state, SampleScan::tablesample, SampleScanState::tsm_state, TableSampleClause::tsmhandler, and SampleScanState::tsmroutine.

Referenced by ExecInitNode().

142 {
143  SampleScanState *scanstate;
144  TableSampleClause *tsc = node->tablesample;
145  TsmRoutine *tsm;
146 
147  Assert(outerPlan(node) == NULL);
148  Assert(innerPlan(node) == NULL);
149 
150  /*
151  * create state structure
152  */
153  scanstate = makeNode(SampleScanState);
154  scanstate->ss.ps.plan = (Plan *) node;
155  scanstate->ss.ps.state = estate;
156 
157  /*
158  * Miscellaneous initialization
159  *
160  * create expression context for node
161  */
162  ExecAssignExprContext(estate, &scanstate->ss.ps);
163 
164  /*
165  * initialize child expressions
166  */
167  scanstate->ss.ps.qual =
168  ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
169 
170  scanstate->args = ExecInitExprList(tsc->args, (PlanState *) scanstate);
171  scanstate->repeatable =
172  ExecInitExpr(tsc->repeatable, (PlanState *) scanstate);
173 
174  /*
175  * tuple table initialization
176  */
177  ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
178  ExecInitScanTupleSlot(estate, &scanstate->ss);
179 
180  /*
181  * initialize scan relation
182  */
183  InitScanRelation(scanstate, estate, eflags);
184 
185  /*
186  * Initialize result tuple type and projection info.
187  */
188  ExecAssignResultTypeFromTL(&scanstate->ss.ps);
189  ExecAssignScanProjectionInfo(&scanstate->ss);
190 
191  /*
192  * If we don't have a REPEATABLE clause, select a random seed. We want to
193  * do this just once, since the seed shouldn't change over rescans.
194  */
195  if (tsc->repeatable == NULL)
196  scanstate->seed = random();
197 
198  /*
199  * Finally, initialize the TABLESAMPLE method handler.
200  */
201  tsm = GetTsmRoutine(tsc->tsmhandler);
202  scanstate->tsmroutine = tsm;
203  scanstate->tsm_state = NULL;
204 
205  if (tsm->InitSampleScan)
206  tsm->InitSampleScan(scanstate, eflags);
207 
208  /* We'll do BeginSampleScan later; we can't evaluate params yet */
209  scanstate->begun = false;
210 
211  return scanstate;
212 }
InitSampleScan_function InitSampleScan
Definition: tsmapi.h:70
List * qual
Definition: plannodes.h:145
Plan plan
Definition: plannodes.h:328
void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate)
Definition: execTuples.c:842
long random(void)
Definition: random.c:22
void * tsm_state
Definition: execnodes.h:1085
struct TableSampleClause * tablesample
Definition: plannodes.h:346
EState * state
Definition: execnodes.h:815
ExprState * ExecInitQual(List *qual, PlanState *parent)
Definition: execExpr.c:160
void ExecAssignResultTypeFromTL(PlanState *planstate)
Definition: execUtils.c:440
PlanState ps
Definition: execnodes.h:1058
void ExecAssignScanProjectionInfo(ScanState *node)
Definition: execScan.c:235
void ExecInitResultTupleSlot(EState *estate, PlanState *planstate)
Definition: execTuples.c:832
Scan scan
Definition: plannodes.h:344
#define innerPlan(node)
Definition: plannodes.h:173
List * ExecInitExprList(List *nodes, PlanState *parent)
Definition: execExpr.c:266
ExprState * repeatable
Definition: execnodes.h:1082
#define outerPlan(node)
Definition: plannodes.h:174
Plan * plan
Definition: execnodes.h:813
TsmRoutine * GetTsmRoutine(Oid tsmhandler)
Definition: tablesample.c:27
#define makeNode(_type_)
Definition: nodes.h:557
#define NULL
Definition: c.h:229
#define Assert(condition)
Definition: c.h:675
static void InitScanRelation(SampleScanState *node, EState *estate, int eflags)
void ExecAssignExprContext(EState *estate, PlanState *planstate)
Definition: execUtils.c:418
struct TsmRoutine * tsmroutine
Definition: execnodes.h:1084
ExprState * qual
Definition: execnodes.h:827
ExprState * ExecInitExpr(Expr *node, PlanState *parent)
Definition: execExpr.c:113
ScanState ss
Definition: execnodes.h:1080
void ExecReScanSampleScan ( SampleScanState node)

Definition at line 260 of file nodeSamplescan.c.

References SampleScanState::begun, ExecScanReScan(), and SampleScanState::ss.

Referenced by ExecReScan().

261 {
262  /* Remember we need to do BeginSampleScan again (if we did it at all) */
263  node->begun = false;
264 
265  ExecScanReScan(&node->ss);
266 }
void ExecScanReScan(ScanState *node)
Definition: execScan.c:327
ScanState ss
Definition: execnodes.h:1080
TupleTableSlot* ExecSampleScan ( SampleScanState node)

Definition at line 100 of file nodeSamplescan.c.

References ExecScan(), SampleNext(), and SampleRecheck().

Referenced by ExecProcNode().

101 {
102  return ExecScan((ScanState *) node,
105 }
TupleTableSlot * ExecScan(ScanState *node, ExecScanAccessMtd accessMtd, ExecScanRecheckMtd recheckMtd)
Definition: execScan.c:121
static TupleTableSlot * SampleNext(SampleScanState *node)
TupleTableSlot *(* ExecScanAccessMtd)(ScanState *node)
Definition: executor.h:389
bool(* ExecScanRecheckMtd)(ScanState *node, TupleTableSlot *slot)
Definition: executor.h:390
static bool SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
static void InitScanRelation ( SampleScanState node,
EState estate,
int  eflags 
)
static

Definition at line 114 of file nodeSamplescan.c.

References ExecAssignScanType(), ExecOpenScanRelation(), NULL, PlanState::plan, ScanState::ps, RelationGetDescr, SampleScanState::ss, ScanState::ss_currentRelation, and ScanState::ss_currentScanDesc.

Referenced by ExecInitSampleScan().

115 {
116  Relation currentRelation;
117 
118  /*
119  * get the relation object id from the relid'th entry in the range table,
120  * open that relation and acquire appropriate lock on it.
121  */
122  currentRelation = ExecOpenScanRelation(estate,
123  ((SampleScan *) node->ss.ps.plan)->scan.scanrelid,
124  eflags);
125 
126  node->ss.ss_currentRelation = currentRelation;
127 
128  /* we won't set up the HeapScanDesc till later */
129  node->ss.ss_currentScanDesc = NULL;
130 
131  /* and report the scan tuple slot's rowtype */
132  ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
133 }
#define RelationGetDescr(relation)
Definition: rel.h:429
Relation ss_currentRelation
Definition: execnodes.h:1059
PlanState ps
Definition: execnodes.h:1058
Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags)
Definition: execUtils.c:603
Plan * plan
Definition: execnodes.h:813
#define NULL
Definition: c.h:229
HeapScanDesc ss_currentScanDesc
Definition: execnodes.h:1060
void ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc)
Definition: execUtils.c:540
ScanState ss
Definition: execnodes.h:1080
static TupleTableSlot * SampleNext ( SampleScanState node)
static

Definition at line 48 of file nodeSamplescan.c.

References SampleScanState::begun, ExecClearTuple(), ExecStoreTuple(), HeapScanDescData::rs_cbuf, SampleScanState::ss, ScanState::ss_currentScanDesc, ScanState::ss_ScanTupleSlot, tablesample_getnext(), and tablesample_init().

Referenced by ExecSampleScan().

49 {
50  HeapTuple tuple;
51  TupleTableSlot *slot;
52 
53  /*
54  * if this is first call within a scan, initialize
55  */
56  if (!node->begun)
57  tablesample_init(node);
58 
59  /*
60  * get the next tuple, and store it in our result slot
61  */
62  tuple = tablesample_getnext(node);
63 
64  slot = node->ss.ss_ScanTupleSlot;
65 
66  if (tuple)
67  ExecStoreTuple(tuple, /* tuple to store */
68  slot, /* slot to store in */
69  node->ss.ss_currentScanDesc->rs_cbuf, /* tuple's buffer */
70  false); /* don't pfree this pointer */
71  else
72  ExecClearTuple(slot);
73 
74  return slot;
75 }
TupleTableSlot * ExecStoreTuple(HeapTuple tuple, TupleTableSlot *slot, Buffer buffer, bool shouldFree)
Definition: execTuples.c:320
TupleTableSlot * ExecClearTuple(TupleTableSlot *slot)
Definition: execTuples.c:439
static HeapTuple tablesample_getnext(SampleScanState *scanstate)
TupleTableSlot * ss_ScanTupleSlot
Definition: execnodes.h:1061
static void tablesample_init(SampleScanState *scanstate)
Buffer rs_cbuf
Definition: relscan.h:70
HeapScanDesc ss_currentScanDesc
Definition: execnodes.h:1060
ScanState ss
Definition: execnodes.h:1080
static bool SampleRecheck ( SampleScanState node,
TupleTableSlot slot 
)
static

Definition at line 81 of file nodeSamplescan.c.

Referenced by ExecSampleScan().

82 {
83  /*
84  * No need to recheck for SampleScan, since like SeqScan we don't pass any
85  * checkable keys to heap_beginscan.
86  */
87  return true;
88 }
static bool SampleTupleVisible ( HeapTuple  tuple,
OffsetNumber  tupoffset,
HeapScanDesc  scan 
)
static

Definition at line 554 of file nodeSamplescan.c.

References HeapTupleSatisfiesVisibility, HeapScanDescData::rs_cbuf, HeapScanDescData::rs_ntuples, HeapScanDescData::rs_pageatatime, HeapScanDescData::rs_snapshot, and HeapScanDescData::rs_vistuples.

Referenced by tablesample_getnext().

555 {
556  if (scan->rs_pageatatime)
557  {
558  /*
559  * In pageatatime mode, heapgetpage() already did visibility checks,
560  * so just look at the info it left in rs_vistuples[].
561  *
562  * We use a binary search over the known-sorted array. Note: we could
563  * save some effort if we insisted that NextSampleTuple select tuples
564  * in increasing order, but it's not clear that there would be enough
565  * gain to justify the restriction.
566  */
567  int start = 0,
568  end = scan->rs_ntuples - 1;
569 
570  while (start <= end)
571  {
572  int mid = (start + end) / 2;
573  OffsetNumber curoffset = scan->rs_vistuples[mid];
574 
575  if (tupoffset == curoffset)
576  return true;
577  else if (tupoffset < curoffset)
578  end = mid - 1;
579  else
580  start = mid + 1;
581  }
582 
583  return false;
584  }
585  else
586  {
587  /* Otherwise, we have to check the tuple individually. */
588  return HeapTupleSatisfiesVisibility(tuple,
589  scan->rs_snapshot,
590  scan->rs_cbuf);
591  }
592 }
#define HeapTupleSatisfiesVisibility(tuple, snapshot, buffer)
Definition: tqual.h:45
uint16 OffsetNumber
Definition: off.h:24
bool rs_pageatatime
Definition: relscan.h:53
Snapshot rs_snapshot
Definition: relscan.h:48
Buffer rs_cbuf
Definition: relscan.h:70
OffsetNumber rs_vistuples[MaxHeapTuplesPerPage]
Definition: relscan.h:77
static HeapTuple tablesample_getnext ( SampleScanState scanstate)
static

Definition at line 377 of file nodeSamplescan.c.

References Assert, BlockNumberIsValid, BUFFER_LOCK_SHARE, BUFFER_LOCK_UNLOCK, BufferGetPage, BufferIsValid, CHECK_FOR_INTERRUPTS, CheckForSerializableConflictOut(), heapgetpage(), InvalidBlockNumber, InvalidBuffer, ItemIdGetLength, ItemIdIsNormal, ItemPointerSet, LockBuffer(), TsmRoutine::NextSampleBlock, TsmRoutine::NextSampleTuple, NULL, OffsetNumberIsValid, PageGetItem, PageGetItemId, PageGetMaxOffsetNumber, PageIsAllVisible, pgstat_count_heap_getnext, ReleaseBuffer(), HeapScanDescData::rs_cblock, HeapScanDescData::rs_cbuf, HeapScanDescData::rs_ctup, HeapScanDescData::rs_inited, HeapScanDescData::rs_nblocks, HeapScanDescData::rs_pageatatime, HeapScanDescData::rs_rd, HeapScanDescData::rs_snapshot, HeapScanDescData::rs_startblock, HeapScanDescData::rs_syncscan, SampleTupleVisible(), SampleScanState::ss, ScanState::ss_currentScanDesc, ss_report_location(), HeapTupleData::t_data, HeapTupleData::t_len, HeapTupleData::t_self, SnapshotData::takenDuringRecovery, and SampleScanState::tsmroutine.

Referenced by SampleNext().

378 {
379  TsmRoutine *tsm = scanstate->tsmroutine;
380  HeapScanDesc scan = scanstate->ss.ss_currentScanDesc;
381  HeapTuple tuple = &(scan->rs_ctup);
382  Snapshot snapshot = scan->rs_snapshot;
383  bool pagemode = scan->rs_pageatatime;
384  BlockNumber blockno;
385  Page page;
386  bool all_visible;
387  OffsetNumber maxoffset;
388 
389  if (!scan->rs_inited)
390  {
391  /*
392  * return null immediately if relation is empty
393  */
394  if (scan->rs_nblocks == 0)
395  {
396  Assert(!BufferIsValid(scan->rs_cbuf));
397  tuple->t_data = NULL;
398  return NULL;
399  }
400  if (tsm->NextSampleBlock)
401  {
402  blockno = tsm->NextSampleBlock(scanstate);
403  if (!BlockNumberIsValid(blockno))
404  {
405  tuple->t_data = NULL;
406  return NULL;
407  }
408  }
409  else
410  blockno = scan->rs_startblock;
411  Assert(blockno < scan->rs_nblocks);
412  heapgetpage(scan, blockno);
413  scan->rs_inited = true;
414  }
415  else
416  {
417  /* continue from previously returned page/tuple */
418  blockno = scan->rs_cblock; /* current page */
419  }
420 
421  /*
422  * When not using pagemode, we must lock the buffer during tuple
423  * visibility checks.
424  */
425  if (!pagemode)
427 
428  page = (Page) BufferGetPage(scan->rs_cbuf);
429  all_visible = PageIsAllVisible(page) && !snapshot->takenDuringRecovery;
430  maxoffset = PageGetMaxOffsetNumber(page);
431 
432  for (;;)
433  {
434  OffsetNumber tupoffset;
435  bool finished;
436 
438 
439  /* Ask the tablesample method which tuples to check on this page. */
440  tupoffset = tsm->NextSampleTuple(scanstate,
441  blockno,
442  maxoffset);
443 
444  if (OffsetNumberIsValid(tupoffset))
445  {
446  ItemId itemid;
447  bool visible;
448 
449  /* Skip invalid tuple pointers. */
450  itemid = PageGetItemId(page, tupoffset);
451  if (!ItemIdIsNormal(itemid))
452  continue;
453 
454  tuple->t_data = (HeapTupleHeader) PageGetItem(page, itemid);
455  tuple->t_len = ItemIdGetLength(itemid);
456  ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
457 
458  if (all_visible)
459  visible = true;
460  else
461  visible = SampleTupleVisible(tuple, tupoffset, scan);
462 
463  /* in pagemode, heapgetpage did this for us */
464  if (!pagemode)
465  CheckForSerializableConflictOut(visible, scan->rs_rd, tuple,
466  scan->rs_cbuf, snapshot);
467 
468  if (visible)
469  {
470  /* Found visible tuple, return it. */
471  if (!pagemode)
473  break;
474  }
475  else
476  {
477  /* Try next tuple from same page. */
478  continue;
479  }
480  }
481 
482  /*
483  * if we get here, it means we've exhausted the items on this page and
484  * it's time to move to the next.
485  */
486  if (!pagemode)
488 
489  if (tsm->NextSampleBlock)
490  {
491  blockno = tsm->NextSampleBlock(scanstate);
492  Assert(!scan->rs_syncscan);
493  finished = !BlockNumberIsValid(blockno);
494  }
495  else
496  {
497  /* Without NextSampleBlock, just do a plain forward seqscan. */
498  blockno++;
499  if (blockno >= scan->rs_nblocks)
500  blockno = 0;
501 
502  /*
503  * Report our new scan position for synchronization purposes.
504  *
505  * Note: we do this before checking for end of scan so that the
506  * final state of the position hint is back at the start of the
507  * rel. That's not strictly necessary, but otherwise when you run
508  * the same query multiple times the starting position would shift
509  * a little bit backwards on every invocation, which is confusing.
510  * We don't guarantee any specific ordering in general, though.
511  */
512  if (scan->rs_syncscan)
513  ss_report_location(scan->rs_rd, blockno);
514 
515  finished = (blockno == scan->rs_startblock);
516  }
517 
518  /*
519  * Reached end of scan?
520  */
521  if (finished)
522  {
523  if (BufferIsValid(scan->rs_cbuf))
524  ReleaseBuffer(scan->rs_cbuf);
525  scan->rs_cbuf = InvalidBuffer;
527  tuple->t_data = NULL;
528  scan->rs_inited = false;
529  return NULL;
530  }
531 
532  Assert(blockno < scan->rs_nblocks);
533  heapgetpage(scan, blockno);
534 
535  /* Re-establish state for new page */
536  if (!pagemode)
538 
539  page = (Page) BufferGetPage(scan->rs_cbuf);
540  all_visible = PageIsAllVisible(page) && !snapshot->takenDuringRecovery;
541  maxoffset = PageGetMaxOffsetNumber(page);
542  }
543 
544  /* Count successfully-fetched tuples as heap fetches */
546 
547  return &(scan->rs_ctup);
548 }
#define BUFFER_LOCK_UNLOCK
Definition: bufmgr.h:87
static bool SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
BlockNumber rs_cblock
Definition: relscan.h:69
#define PageIsAllVisible(page)
Definition: bufpage.h:382
HeapTupleHeaderData * HeapTupleHeader
Definition: htup.h:23
#define InvalidBuffer
Definition: buf.h:25
void heapgetpage(HeapScanDesc scan, BlockNumber page)
Definition: heapam.c:345
uint32 BlockNumber
Definition: block.h:31
void ReleaseBuffer(Buffer buffer)
Definition: bufmgr.c:3309
#define PageGetMaxOffsetNumber(page)
Definition: bufpage.h:354
void CheckForSerializableConflictOut(bool visible, Relation relation, HeapTuple tuple, Buffer buffer, Snapshot snapshot)
Definition: predicate.c:3926
HeapTupleData rs_ctup
Definition: relscan.h:68
uint16 OffsetNumber
Definition: off.h:24
HeapTupleHeader t_data
Definition: htup.h:67
#define ItemIdGetLength(itemId)
Definition: itemid.h:58
NextSampleTuple_function NextSampleTuple
Definition: tsmapi.h:73
bool rs_pageatatime
Definition: relscan.h:53
ItemPointerData t_self
Definition: htup.h:65
uint32 t_len
Definition: htup.h:64
Snapshot rs_snapshot
Definition: relscan.h:48
bool rs_inited
Definition: relscan.h:67
NextSampleBlock_function NextSampleBlock
Definition: tsmapi.h:72
#define BufferGetPage(buffer)
Definition: bufmgr.h:160
BlockNumber rs_startblock
Definition: relscan.h:60
#define PageGetItemId(page, offsetNumber)
Definition: bufpage.h:232
BlockNumber rs_nblocks
Definition: relscan.h:59
void LockBuffer(Buffer buffer, int mode)
Definition: bufmgr.c:3546
Relation rs_rd
Definition: relscan.h:47
#define BlockNumberIsValid(blockNumber)
Definition: block.h:70
Buffer rs_cbuf
Definition: relscan.h:70
#define NULL
Definition: c.h:229
#define Assert(condition)
Definition: c.h:675
#define ItemIdIsNormal(itemId)
Definition: itemid.h:98
bool takenDuringRecovery
Definition: snapshot.h:93
#define InvalidBlockNumber
Definition: block.h:33
#define BufferIsValid(bufnum)
Definition: bufmgr.h:114
struct TsmRoutine * tsmroutine
Definition: execnodes.h:1084
void ss_report_location(Relation rel, BlockNumber location)
Definition: syncscan.c:288
HeapScanDesc ss_currentScanDesc
Definition: execnodes.h:1060
#define OffsetNumberIsValid(offsetNumber)
Definition: off.h:40
#define BUFFER_LOCK_SHARE
Definition: bufmgr.h:88
bool rs_syncscan
Definition: relscan.h:64
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:97
#define pgstat_count_heap_getnext(rel)
Definition: pgstat.h:1253
#define PageGetItem(page, itemId)
Definition: bufpage.h:337
Pointer Page
Definition: bufpage.h:74
#define ItemPointerSet(pointer, blockNumber, offNum)
Definition: itemptr.h:104
ScanState ss
Definition: execnodes.h:1080
static void tablesample_init ( SampleScanState scanstate)
static

Definition at line 273 of file nodeSamplescan.c.

References arg, SampleScanState::args, TsmRoutine::BeginSampleScan, SampleScanState::begun, DatumGetUInt32, DirectFunctionCall1, ereport, errcode(), errmsg(), ERROR, EState::es_snapshot, ExecEvalExprSwitchContext(), hashfloat8(), heap_beginscan_sampling(), heap_rescan_set_params(), i, lfirst, list_length(), TsmRoutine::NextSampleBlock, NULL, palloc(), pfree(), ScanState::ps, PlanState::ps_ExprContext, SampleScanState::repeatable, SampleScanState::seed, SampleScanState::ss, ScanState::ss_currentRelation, ScanState::ss_currentScanDesc, PlanState::state, SampleScanState::tsmroutine, SampleScanState::use_bulkread, and SampleScanState::use_pagemode.

Referenced by SampleNext().

274 {
275  TsmRoutine *tsm = scanstate->tsmroutine;
276  ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
277  Datum *params;
278  Datum datum;
279  bool isnull;
280  uint32 seed;
281  bool allow_sync;
282  int i;
283  ListCell *arg;
284 
285  params = (Datum *) palloc(list_length(scanstate->args) * sizeof(Datum));
286 
287  i = 0;
288  foreach(arg, scanstate->args)
289  {
290  ExprState *argstate = (ExprState *) lfirst(arg);
291 
292  params[i] = ExecEvalExprSwitchContext(argstate,
293  econtext,
294  &isnull);
295  if (isnull)
296  ereport(ERROR,
297  (errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
298  errmsg("TABLESAMPLE parameter cannot be null")));
299  i++;
300  }
301 
302  if (scanstate->repeatable)
303  {
304  datum = ExecEvalExprSwitchContext(scanstate->repeatable,
305  econtext,
306  &isnull);
307  if (isnull)
308  ereport(ERROR,
309  (errcode(ERRCODE_INVALID_TABLESAMPLE_REPEAT),
310  errmsg("TABLESAMPLE REPEATABLE parameter cannot be null")));
311 
312  /*
313  * The REPEATABLE parameter has been coerced to float8 by the parser.
314  * The reason for using float8 at the SQL level is that it will
315  * produce unsurprising results both for users used to databases that
316  * accept only integers in the REPEATABLE clause and for those who
317  * might expect that REPEATABLE works like setseed() (a float in the
318  * range from -1 to 1).
319  *
320  * We use hashfloat8() to convert the supplied value into a suitable
321  * seed. For regression-testing purposes, that has the convenient
322  * property that REPEATABLE(0) gives a machine-independent result.
323  */
325  }
326  else
327  {
328  /* Use the seed selected by ExecInitSampleScan */
329  seed = scanstate->seed;
330  }
331 
332  /* Set default values for params that BeginSampleScan can adjust */
333  scanstate->use_bulkread = true;
334  scanstate->use_pagemode = true;
335 
336  /* Let tablesample method do its thing */
337  tsm->BeginSampleScan(scanstate,
338  params,
339  list_length(scanstate->args),
340  seed);
341 
342  /* We'll use syncscan if there's no NextSampleBlock function */
343  allow_sync = (tsm->NextSampleBlock == NULL);
344 
345  /* Now we can create or reset the HeapScanDesc */
346  if (scanstate->ss.ss_currentScanDesc == NULL)
347  {
348  scanstate->ss.ss_currentScanDesc =
350  scanstate->ss.ps.state->es_snapshot,
351  0, NULL,
352  scanstate->use_bulkread,
353  allow_sync,
354  scanstate->use_pagemode);
355  }
356  else
357  {
359  scanstate->use_bulkread,
360  allow_sync,
361  scanstate->use_pagemode);
362  }
363 
364  pfree(params);
365 
366  /* And we're initialized. */
367  scanstate->begun = true;
368 }
#define DatumGetUInt32(X)
Definition: postgres.h:492
static Datum ExecEvalExprSwitchContext(ExprState *state, ExprContext *econtext, bool *isNull)
Definition: executor.h:281
ExprContext * ps_ExprContext
Definition: execnodes.h:843
int errcode(int sqlerrcode)
Definition: elog.c:575
Snapshot es_snapshot
Definition: execnodes.h:409
#define DirectFunctionCall1(func, arg1)
Definition: fmgr.h:584
Relation ss_currentRelation
Definition: execnodes.h:1059
EState * state
Definition: execnodes.h:815
PlanState ps
Definition: execnodes.h:1058
void pfree(void *pointer)
Definition: mcxt.c:950
#define ERROR
Definition: elog.h:43
HeapScanDesc heap_beginscan_sampling(Relation relation, Snapshot snapshot, int nkeys, ScanKey key, bool allow_strat, bool allow_sync, bool allow_pagemode)
Definition: heapam.c:1427
unsigned int uint32
Definition: c.h:268
ExprState * repeatable
Definition: execnodes.h:1082
NextSampleBlock_function NextSampleBlock
Definition: tsmapi.h:72
#define ereport(elevel, rest)
Definition: elog.h:122
Datum hashfloat8(PG_FUNCTION_ARGS)
Definition: hashfunc.c:120
uintptr_t Datum
Definition: postgres.h:372
#define NULL
Definition: c.h:229
#define lfirst(lc)
Definition: pg_list.h:106
void heap_rescan_set_params(HeapScanDesc scan, ScanKey key, bool allow_strat, bool allow_sync, bool allow_pagemode)
Definition: heapam.c:1559
static int list_length(const List *l)
Definition: pg_list.h:89
struct TsmRoutine * tsmroutine
Definition: execnodes.h:1084
BeginSampleScan_function BeginSampleScan
Definition: tsmapi.h:71
HeapScanDesc ss_currentScanDesc
Definition: execnodes.h:1060
void * palloc(Size size)
Definition: mcxt.c:849
int errmsg(const char *fmt,...)
Definition: elog.c:797
int i
void * arg
ScanState ss
Definition: execnodes.h:1080