Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * nodeRecursiveunion.c
4 : * routines to handle RecursiveUnion nodes.
5 : *
6 : * To implement UNION (without ALL), we need a hashtable that stores tuples
7 : * already seen. The hash key is computed from the grouping columns.
8 : *
9 : *
10 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
11 : * Portions Copyright (c) 1994, Regents of the University of California
12 : *
13 : *
14 : * IDENTIFICATION
15 : * src/backend/executor/nodeRecursiveunion.c
16 : *
17 : *-------------------------------------------------------------------------
18 : */
19 : #include "postgres.h"
20 :
21 : #include "executor/executor.h"
22 : #include "executor/nodeRecursiveunion.h"
23 : #include "miscadmin.h"
24 : #include "utils/memutils.h"
25 : #include "utils/tuplestore.h"
26 :
27 :
28 :
29 : /*
30 : * Initialize the hash table to empty.
31 : */
32 : static void
33 273 : build_hash_table(RecursiveUnionState *rustate)
34 : {
35 273 : RecursiveUnion *node = (RecursiveUnion *) rustate->ps.plan;
36 273 : TupleDesc desc = ExecGetResultType(outerPlanState(rustate));
37 :
38 : Assert(node->numCols > 0);
39 :
40 : /*
41 : * If both child plans deliver the same fixed tuple slot type, we can tell
42 : * BuildTupleHashTable to expect that slot type as input. Otherwise,
43 : * we'll pass NULL denoting that any slot type is possible.
44 : */
45 273 : rustate->hashtable = BuildTupleHashTable(&rustate->ps,
46 : desc,
47 : ExecGetCommonChildSlotOps(&rustate->ps),
48 : node->numCols,
49 : node->dupColIdx,
50 273 : rustate->eqfuncoids,
51 : rustate->hashfunctions,
52 : node->dupCollations,
53 : node->numGroups,
54 : 0,
55 273 : rustate->ps.state->es_query_cxt,
56 : rustate->tuplesContext,
57 : rustate->tempContext,
58 : false);
59 273 : }
60 :
61 :
62 : /* ----------------------------------------------------------------
63 : * ExecRecursiveUnion(node)
64 : *
65 : * Scans the recursive query sequentially and returns the next
66 : * qualifying tuple.
67 : *
68 : * 1. evaluate non recursive term and assign the result to RT
69 : *
70 : * 2. execute recursive terms
71 : *
72 : * 2.1 WT := RT
73 : * 2.2 while WT is not empty repeat 2.3 to 2.6. if WT is empty returns RT
74 : * 2.3 replace the name of recursive term with WT
75 : * 2.4 evaluate the recursive term and store into WT
76 : * 2.5 append WT to RT
77 : * 2.6 go back to 2.2
78 : * ----------------------------------------------------------------
79 : */
80 : static TupleTableSlot *
81 41348 : ExecRecursiveUnion(PlanState *pstate)
82 : {
83 41348 : RecursiveUnionState *node = castNode(RecursiveUnionState, pstate);
84 41348 : PlanState *outerPlan = outerPlanState(node);
85 41348 : PlanState *innerPlan = innerPlanState(node);
86 41348 : RecursiveUnion *plan = (RecursiveUnion *) node->ps.plan;
87 : TupleTableSlot *slot;
88 : bool isnew;
89 :
90 41348 : CHECK_FOR_INTERRUPTS();
91 :
92 : /* 1. Evaluate non-recursive term */
93 41348 : if (!node->recursing)
94 : {
95 : for (;;)
96 : {
97 13131 : slot = ExecProcNode(outerPlan);
98 13131 : if (TupIsNull(slot))
99 : break;
100 12548 : if (plan->numCols > 0)
101 : {
102 : /* Find or build hashtable entry for this tuple's group */
103 293 : LookupTupleHashEntry(node->hashtable, slot, &isnew, NULL);
104 : /* Must reset temp context after each hashtable lookup */
105 293 : MemoryContextReset(node->tempContext);
106 : /* Ignore tuple if already seen */
107 293 : if (!isnew)
108 10 : continue;
109 : }
110 : /* Each non-duplicate tuple goes to the working table ... */
111 12538 : tuplestore_puttupleslot(node->working_table, slot);
112 : /* ... and to the caller */
113 12538 : return slot;
114 : }
115 583 : node->recursing = true;
116 : }
117 :
118 : /* 2. Execute recursive term */
119 : for (;;)
120 : {
121 33132 : slot = ExecProcNode(innerPlan);
122 33132 : if (TupIsNull(slot))
123 4272 : {
124 : Tuplestorestate *swaptemp;
125 :
126 : /* Done if there's nothing in the intermediate table */
127 4827 : if (node->intermediate_empty)
128 555 : break;
129 :
130 : /*
131 : * Now we let the intermediate table become the work table. We
132 : * need a fresh intermediate table, so delete the tuples from the
133 : * current working table and use that as the new intermediate
134 : * table. This saves a round of free/malloc from creating a new
135 : * tuple store.
136 : */
137 4272 : tuplestore_clear(node->working_table);
138 :
139 4272 : swaptemp = node->working_table;
140 4272 : node->working_table = node->intermediate_table;
141 4272 : node->intermediate_table = swaptemp;
142 :
143 : /* mark the intermediate table as empty */
144 4272 : node->intermediate_empty = true;
145 :
146 : /* reset the recursive term */
147 4272 : innerPlan->chgParam = bms_add_member(innerPlan->chgParam,
148 : plan->wtParam);
149 :
150 : /* and continue fetching from recursive term */
151 4272 : continue;
152 : }
153 :
154 28305 : if (plan->numCols > 0)
155 : {
156 : /* Find or build hashtable entry for this tuple's group */
157 558 : LookupTupleHashEntry(node->hashtable, slot, &isnew, NULL);
158 : /* Must reset temp context after each hashtable lookup */
159 558 : MemoryContextReset(node->tempContext);
160 : /* Ignore tuple if already seen */
161 558 : if (!isnew)
162 50 : continue;
163 : }
164 :
165 : /* Else, tuple is good; stash it in intermediate table ... */
166 28255 : node->intermediate_empty = false;
167 28255 : tuplestore_puttupleslot(node->intermediate_table, slot);
168 : /* ... and return it */
169 28255 : return slot;
170 : }
171 :
172 555 : return NULL;
173 : }
174 :
175 : /* ----------------------------------------------------------------
176 : * ExecInitRecursiveUnion
177 : * ----------------------------------------------------------------
178 : */
179 : RecursiveUnionState *
180 615 : ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
181 : {
182 : RecursiveUnionState *rustate;
183 : ParamExecData *prmdata;
184 :
185 : /* check for unsupported flags */
186 : Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
187 :
188 : /*
189 : * create state structure
190 : */
191 615 : rustate = makeNode(RecursiveUnionState);
192 615 : rustate->ps.plan = (Plan *) node;
193 615 : rustate->ps.state = estate;
194 615 : rustate->ps.ExecProcNode = ExecRecursiveUnion;
195 :
196 615 : rustate->eqfuncoids = NULL;
197 615 : rustate->hashfunctions = NULL;
198 615 : rustate->hashtable = NULL;
199 615 : rustate->tempContext = NULL;
200 615 : rustate->tuplesContext = NULL;
201 :
202 : /* initialize processing state */
203 615 : rustate->recursing = false;
204 615 : rustate->intermediate_empty = true;
205 615 : rustate->working_table = tuplestore_begin_heap(false, false, work_mem);
206 615 : rustate->intermediate_table = tuplestore_begin_heap(false, false, work_mem);
207 :
208 : /*
209 : * If hashing, we need a per-tuple memory context for comparisons, and a
210 : * longer-lived context to store the hash table. The table can't just be
211 : * kept in the per-query context because we want to be able to throw it
212 : * away when rescanning. We can use a BumpContext to save storage,
213 : * because we will have no need to delete individual table entries.
214 : */
215 615 : if (node->numCols > 0)
216 : {
217 273 : rustate->tempContext =
218 273 : AllocSetContextCreate(CurrentMemoryContext,
219 : "RecursiveUnion",
220 : ALLOCSET_DEFAULT_SIZES);
221 273 : rustate->tuplesContext =
222 273 : BumpContextCreate(CurrentMemoryContext,
223 : "RecursiveUnion hashed tuples",
224 : ALLOCSET_DEFAULT_SIZES);
225 : }
226 :
227 : /*
228 : * Make the state structure available to descendant WorkTableScan nodes
229 : * via the Param slot reserved for it.
230 : */
231 615 : prmdata = &(estate->es_param_exec_vals[node->wtParam]);
232 : Assert(prmdata->execPlan == NULL);
233 615 : prmdata->value = PointerGetDatum(rustate);
234 615 : prmdata->isnull = false;
235 :
236 : /*
237 : * Miscellaneous initialization
238 : *
239 : * RecursiveUnion plans don't have expression contexts because they never
240 : * call ExecQual or ExecProject.
241 : */
242 : Assert(node->plan.qual == NIL);
243 :
244 : /*
245 : * RecursiveUnion nodes still have Result slots, which hold pointers to
246 : * tuples, so we have to initialize them.
247 : */
248 615 : ExecInitResultTypeTL(&rustate->ps);
249 :
250 : /*
251 : * Initialize result tuple type. (Note: we have to set up the result type
252 : * before initializing child nodes, because nodeWorktablescan.c expects it
253 : * to be valid.)
254 : */
255 615 : rustate->ps.ps_ProjInfo = NULL;
256 :
257 : /*
258 : * initialize child nodes
259 : */
260 615 : outerPlanState(rustate) = ExecInitNode(outerPlan(node), estate, eflags);
261 615 : innerPlanState(rustate) = ExecInitNode(innerPlan(node), estate, eflags);
262 :
263 : /*
264 : * If hashing, precompute fmgr lookup data for inner loop, and create the
265 : * hash table.
266 : */
267 615 : if (node->numCols > 0)
268 : {
269 273 : execTuplesHashPrepare(node->numCols,
270 273 : node->dupOperators,
271 : &rustate->eqfuncoids,
272 : &rustate->hashfunctions);
273 273 : build_hash_table(rustate);
274 : }
275 :
276 615 : return rustate;
277 : }
278 :
279 : /* ----------------------------------------------------------------
280 : * ExecEndRecursiveUnion
281 : *
282 : * frees any storage allocated through C routines.
283 : * ----------------------------------------------------------------
284 : */
285 : void
286 615 : ExecEndRecursiveUnion(RecursiveUnionState *node)
287 : {
288 : /* Release tuplestores */
289 615 : tuplestore_end(node->working_table);
290 615 : tuplestore_end(node->intermediate_table);
291 :
292 : /* free subsidiary stuff including hashtable data */
293 615 : if (node->tempContext)
294 273 : MemoryContextDelete(node->tempContext);
295 615 : if (node->tuplesContext)
296 273 : MemoryContextDelete(node->tuplesContext);
297 :
298 : /*
299 : * close down subplans
300 : */
301 615 : ExecEndNode(outerPlanState(node));
302 615 : ExecEndNode(innerPlanState(node));
303 615 : }
304 :
305 : /* ----------------------------------------------------------------
306 : * ExecReScanRecursiveUnion
307 : *
308 : * Rescans the relation.
309 : * ----------------------------------------------------------------
310 : */
311 : void
312 8 : ExecReScanRecursiveUnion(RecursiveUnionState *node)
313 : {
314 8 : PlanState *outerPlan = outerPlanState(node);
315 8 : PlanState *innerPlan = innerPlanState(node);
316 8 : RecursiveUnion *plan = (RecursiveUnion *) node->ps.plan;
317 :
318 : /*
319 : * Set recursive term's chgParam to tell it that we'll modify the working
320 : * table and therefore it has to rescan.
321 : */
322 8 : innerPlan->chgParam = bms_add_member(innerPlan->chgParam, plan->wtParam);
323 :
324 : /*
325 : * if chgParam of subnode is not null then plan will be re-scanned by
326 : * first ExecProcNode. Because of above, we only have to do this to the
327 : * non-recursive term.
328 : */
329 8 : if (outerPlan->chgParam == NULL)
330 0 : ExecReScan(outerPlan);
331 :
332 : /* Empty hashtable if needed */
333 8 : if (plan->numCols > 0)
334 8 : ResetTupleHashTable(node->hashtable);
335 :
336 : /* reset processing state */
337 8 : node->recursing = false;
338 8 : node->intermediate_empty = true;
339 8 : tuplestore_clear(node->working_table);
340 8 : tuplestore_clear(node->intermediate_table);
341 8 : }
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