1/*-------------------------------------------------------------------------
2 *
3 * tsmapi.h
4 * API for tablesample methods
5 *
6 * Copyright (c) 2015-2019, 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/pathnodes.h"
17
18
19/*
20 * Callback function signatures --- see tablesample-method.sgml for more info.
21 */
22
23typedef void (*SampleScanGetSampleSize_function) (PlannerInfo *root,
24 RelOptInfo *baserel,
25 List *paramexprs,
26 BlockNumber *pages,
27 double *tuples);
28
29typedef void (*InitSampleScan_function) (SampleScanState *node,
30 int eflags);
31
32typedef void (*BeginSampleScan_function) (SampleScanState *node,
33 Datum *params,
34 int nparams,
35 uint32 seed);
36
37typedef BlockNumber (*NextSampleBlock_function) (SampleScanState *node,
38 BlockNumber nblocks);
39
40typedef OffsetNumber (*NextSampleTuple_function) (SampleScanState *node,
41 BlockNumber blockno,
42 OffsetNumber maxoffset);
43
44typedef void (*EndSampleScan_function) (SampleScanState *node);
45
46/*
47 * TsmRoutine is the struct returned by a tablesample method's handler
48 * function. It provides pointers to the callback functions needed by the
49 * planner and executor, as well as additional information about the method.
50 *
51 * More function pointers are likely to be added in the future.
52 * Therefore it's recommended that the handler initialize the struct with
53 * makeNode(TsmRoutine) so that all fields are set to NULL. This will
54 * ensure that no fields are accidentally left undefined.
55 */
56typedef struct TsmRoutine
57{
58 NodeTag type;
59
60 /* List of datatype OIDs for the arguments of the TABLESAMPLE clause */
61 List *parameterTypes;
62
63 /* Can method produce repeatable samples across, or even within, queries? */
64 bool repeatable_across_queries;
65 bool repeatable_across_scans;
66
67 /* Functions for planning a SampleScan on a physical table */
68 SampleScanGetSampleSize_function SampleScanGetSampleSize;
69
70 /* Functions for executing a SampleScan on a physical table */
71 InitSampleScan_function InitSampleScan; /* can be NULL */
72 BeginSampleScan_function BeginSampleScan;
73 NextSampleBlock_function NextSampleBlock; /* can be NULL */
74 NextSampleTuple_function NextSampleTuple;
75 EndSampleScan_function EndSampleScan; /* can be NULL */
76} TsmRoutine;
77
78
79/* Functions in access/tablesample/tablesample.c */
80extern TsmRoutine *GetTsmRoutine(Oid tsmhandler);
81
82#endif /* TSMAPI_H */
83