granicus.if.org Git - postgresql/blob - src/include/access/tsmapi.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * tsmapi.h
   4  *        API for tablesample methods
   5  *
   6  * Copyright (c) 2015-2017, PostgreSQL Global Development Group
   7  *
   8  * src/include/access/tsmapi.h
   9  *
  10  *-------------------------------------------------------------------------
  11  */
  12 #ifndef TSMAPI_H
  13 #define TSMAPI_H
  14
  15 #include "nodes/execnodes.h"
  16 #include "nodes/relation.h"
  17
  18
  19 /*
  20  * Callback function signatures --- see tablesample-method.sgml for more info.
  21  */
  22
  23 typedef void (*SampleScanGetSampleSize_function) (PlannerInfo *root,
  24                                                                                                   RelOptInfo *baserel,
  25                                                                                                   List *paramexprs,
  26                                                                                                   BlockNumber *pages,
  27                                                                                                   double *tuples);
  28
  29 typedef void (*InitSampleScan_function) (SampleScanState *node,
  30                                                                                  int eflags);
  31
  32 typedef void (*BeginSampleScan_function) (SampleScanState *node,
  33                                                                                   Datum *params,
  34                                                                                   int nparams,
  35                                                                                   uint32 seed);
  36
  37 typedef BlockNumber (*NextSampleBlock_function) (SampleScanState *node);
  38
  39 typedef OffsetNumber (*NextSampleTuple_function) (SampleScanState *node,
  40                                                                                                   BlockNumber blockno,
  41                                                                                                   OffsetNumber maxoffset);
  42
  43 typedef void (*EndSampleScan_function) (SampleScanState *node);
  44
  45 /*
  46  * TsmRoutine is the struct returned by a tablesample method's handler
  47  * function.  It provides pointers to the callback functions needed by the
  48  * planner and executor, as well as additional information about the method.
  49  *
  50  * More function pointers are likely to be added in the future.
  51  * Therefore it's recommended that the handler initialize the struct with
  52  * makeNode(TsmRoutine) so that all fields are set to NULL.  This will
  53  * ensure that no fields are accidentally left undefined.
  54  */
  55 typedef struct TsmRoutine
  56 {
  57         NodeTag         type;
  58
  59         /* List of datatype OIDs for the arguments of the TABLESAMPLE clause */
  60         List       *parameterTypes;
  61
  62         /* Can method produce repeatable samples across, or even within, queries? */
  63         bool            repeatable_across_queries;
  64         bool            repeatable_across_scans;
  65
  66         /* Functions for planning a SampleScan on a physical table */
  67         SampleScanGetSampleSize_function SampleScanGetSampleSize;
  68
  69         /* Functions for executing a SampleScan on a physical table */
  70         InitSampleScan_function InitSampleScan; /* can be NULL */
  71         BeginSampleScan_function BeginSampleScan;
  72         NextSampleBlock_function NextSampleBlock;       /* can be NULL */
  73         NextSampleTuple_function NextSampleTuple;
  74         EndSampleScan_function EndSampleScan;   /* can be NULL */
  75 } TsmRoutine;
  76
  77
  78 /* Functions in access/tablesample/tablesample.c */
  79 extern TsmRoutine *GetTsmRoutine(Oid tsmhandler);
  80
  81 #endif                                                  /* TSMAPI_H */