1/*-------------------------------------------------------------------------
2 *
3 * nodeNamedtuplestorescan.c
4 * routines to handle NamedTuplestoreScan nodes.
5 *
6 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
8 *
9 *
10 * IDENTIFICATION
11 * src/backend/executor/nodeNamedtuplestorescan.c
12 *
13 *-------------------------------------------------------------------------
14 */
15
16#include "postgres.h"
17
18#include "executor/execdebug.h"
19#include "executor/nodeNamedtuplestorescan.h"
20#include "miscadmin.h"
21#include "utils/queryenvironment.h"
22
23static TupleTableSlot *NamedTuplestoreScanNext(NamedTuplestoreScanState *node);
24
25/* ----------------------------------------------------------------
26 * NamedTuplestoreScanNext
27 *
28 * This is a workhorse for ExecNamedTuplestoreScan
29 * ----------------------------------------------------------------
30 */
31static TupleTableSlot *
32NamedTuplestoreScanNext(NamedTuplestoreScanState *node)
33{
34 TupleTableSlot *slot;
35
36 /* We intentionally do not support backward scan. */
37 Assert(ScanDirectionIsForward(node->ss.ps.state->es_direction));
38
39 /*
40 * Get the next tuple from tuplestore. Return NULL if no more tuples.
41 */
42 slot = node->ss.ss_ScanTupleSlot;
43 tuplestore_select_read_pointer(node->relation, node->readptr);
44 (void) tuplestore_gettupleslot(node->relation, true, false, slot);
45 return slot;
46}
47
48/*
49 * NamedTuplestoreScanRecheck -- access method routine to recheck a tuple in
50 * EvalPlanQual
51 */
52static bool
53NamedTuplestoreScanRecheck(NamedTuplestoreScanState *node, TupleTableSlot *slot)
54{
55 /* nothing to check */
56 return true;
57}
58
59/* ----------------------------------------------------------------
60 * ExecNamedTuplestoreScan(node)
61 *
62 * Scans the CTE sequentially and returns the next qualifying tuple.
63 * We call the ExecScan() routine and pass it the appropriate
64 * access method functions.
65 * ----------------------------------------------------------------
66 */
67static TupleTableSlot *
68ExecNamedTuplestoreScan(PlanState *pstate)
69{
70 NamedTuplestoreScanState *node = castNode(NamedTuplestoreScanState, pstate);
71
72 return ExecScan(&node->ss,
73 (ExecScanAccessMtd) NamedTuplestoreScanNext,
74 (ExecScanRecheckMtd) NamedTuplestoreScanRecheck);
75}
76
77
78/* ----------------------------------------------------------------
79 * ExecInitNamedTuplestoreScan
80 * ----------------------------------------------------------------
81 */
82NamedTuplestoreScanState *
83ExecInitNamedTuplestoreScan(NamedTuplestoreScan *node, EState *estate, int eflags)
84{
85 NamedTuplestoreScanState *scanstate;
86 EphemeralNamedRelation enr;
87
88 /* check for unsupported flags */
89 Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
90
91 /*
92 * NamedTuplestoreScan should not have any children.
93 */
94 Assert(outerPlan(node) == NULL);
95 Assert(innerPlan(node) == NULL);
96
97 /*
98 * create new NamedTuplestoreScanState for node
99 */
100 scanstate = makeNode(NamedTuplestoreScanState);
101 scanstate->ss.ps.plan = (Plan *) node;
102 scanstate->ss.ps.state = estate;
103 scanstate->ss.ps.ExecProcNode = ExecNamedTuplestoreScan;
104
105 enr = get_ENR(estate->es_queryEnv, node->enrname);
106 if (!enr)
107 elog(ERROR, "executor could not find named tuplestore \"%s\"",
108 node->enrname);
109
110 Assert(enr->reldata);
111 scanstate->relation = (Tuplestorestate *) enr->reldata;
112 scanstate->tupdesc = ENRMetadataGetTupDesc(&(enr->md));
113 scanstate->readptr =
114 tuplestore_alloc_read_pointer(scanstate->relation, EXEC_FLAG_REWIND);
115
116 /*
117 * The new read pointer copies its position from read pointer 0, which
118 * could be anywhere, so explicitly rewind it.
119 */
120 tuplestore_select_read_pointer(scanstate->relation, scanstate->readptr);
121 tuplestore_rescan(scanstate->relation);
122
123 /*
124 * XXX: Should we add a function to free that read pointer when done?
125 *
126 * This was attempted, but it did not improve performance or memory usage
127 * in any tested cases.
128 */
129
130 /*
131 * Miscellaneous initialization
132 *
133 * create expression context for node
134 */
135 ExecAssignExprContext(estate, &scanstate->ss.ps);
136
137 /*
138 * The scan tuple type is specified for the tuplestore.
139 */
140 ExecInitScanTupleSlot(estate, &scanstate->ss, scanstate->tupdesc,
141 &TTSOpsMinimalTuple);
142
143 /*
144 * Initialize result type and projection.
145 */
146 ExecInitResultTypeTL(&scanstate->ss.ps);
147 ExecAssignScanProjectionInfo(&scanstate->ss);
148
149 /*
150 * initialize child expressions
151 */
152 scanstate->ss.ps.qual =
153 ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
154
155 return scanstate;
156}
157
158/* ----------------------------------------------------------------
159 * ExecEndNamedTuplestoreScan
160 *
161 * frees any storage allocated through C routines.
162 * ----------------------------------------------------------------
163 */
164void
165ExecEndNamedTuplestoreScan(NamedTuplestoreScanState *node)
166{
167 /*
168 * Free exprcontext
169 */
170 ExecFreeExprContext(&node->ss.ps);
171
172 /*
173 * clean out the tuple table
174 */
175 if (node->ss.ps.ps_ResultTupleSlot)
176 ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
177 ExecClearTuple(node->ss.ss_ScanTupleSlot);
178}
179
180/* ----------------------------------------------------------------
181 * ExecReScanNamedTuplestoreScan
182 *
183 * Rescans the relation.
184 * ----------------------------------------------------------------
185 */
186void
187ExecReScanNamedTuplestoreScan(NamedTuplestoreScanState *node)
188{
189 Tuplestorestate *tuplestorestate = node->relation;
190
191 if (node->ss.ps.ps_ResultTupleSlot)
192 ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
193
194 ExecScanReScan(&node->ss);
195
196 /*
197 * Rewind my own pointer.
198 */
199 tuplestore_select_read_pointer(tuplestorestate, node->readptr);
200 tuplestore_rescan(tuplestorestate);
201}
202