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 :
26 :
27 :
28 : /*
29 : * Initialize the hash table to empty.
30 : */
31 : static void
32 251 : build_hash_table(RecursiveUnionState *rustate)
33 : {
34 251 : RecursiveUnion *node = (RecursiveUnion *) rustate->ps.plan;
35 251 : TupleDesc desc = ExecGetResultType(outerPlanState(rustate));
36 :
37 : Assert(node->numCols > 0);
38 :
39 : /*
40 : * If both child plans deliver the same fixed tuple slot type, we can tell
41 : * BuildTupleHashTable to expect that slot type as input. Otherwise,
42 : * we'll pass NULL denoting that any slot type is possible.
43 : */
44 251 : rustate->hashtable = BuildTupleHashTable(&rustate->ps,
45 : desc,
46 : ExecGetCommonChildSlotOps(&rustate->ps),
47 : node->numCols,
48 : node->dupColIdx,
49 251 : rustate->eqfuncoids,
50 : rustate->hashfunctions,
51 : node->dupCollations,
52 : node->numGroups,
53 : 0,
54 251 : rustate->ps.state->es_query_cxt,
55 : rustate->tuplesContext,
56 : rustate->tempContext,
57 : false);
58 251 : }
59 :
60 :
61 : /* ----------------------------------------------------------------
62 : * ExecRecursiveUnion(node)
63 : *
64 : * Scans the recursive query sequentially and returns the next
65 : * qualifying tuple.
66 : *
67 : * 1. evaluate non recursive term and assign the result to RT
68 : *
69 : * 2. execute recursive terms
70 : *
71 : * 2.1 WT := RT
72 : * 2.2 while WT is not empty repeat 2.3 to 2.6. if WT is empty returns RT
73 : * 2.3 replace the name of recursive term with WT
74 : * 2.4 evaluate the recursive term and store into WT
75 : * 2.5 append WT to RT
76 : * 2.6 go back to 2.2
77 : * ----------------------------------------------------------------
78 : */
79 : static TupleTableSlot *
80 36641 : ExecRecursiveUnion(PlanState *pstate)
81 : {
82 36641 : RecursiveUnionState *node = castNode(RecursiveUnionState, pstate);
83 36641 : PlanState *outerPlan = outerPlanState(node);
84 36641 : PlanState *innerPlan = innerPlanState(node);
85 36641 : RecursiveUnion *plan = (RecursiveUnion *) node->ps.plan;
86 : TupleTableSlot *slot;
87 : bool isnew;
88 :
89 36641 : CHECK_FOR_INTERRUPTS();
90 :
91 : /* 1. Evaluate non-recursive term */
92 36641 : if (!node->recursing)
93 : {
94 : for (;;)
95 : {
96 11610 : slot = ExecProcNode(outerPlan);
97 11610 : if (TupIsNull(slot))
98 : break;
99 11105 : if (plan->numCols > 0)
100 : {
101 : /* Find or build hashtable entry for this tuple's group */
102 261 : LookupTupleHashEntry(node->hashtable, slot, &isnew, NULL);
103 : /* Must reset temp context after each hashtable lookup */
104 261 : MemoryContextReset(node->tempContext);
105 : /* Ignore tuple if already seen */
106 261 : if (!isnew)
107 9 : continue;
108 : }
109 : /* Each non-duplicate tuple goes to the working table ... */
110 11096 : tuplestore_puttupleslot(node->working_table, slot);
111 : /* ... and to the caller */
112 11096 : return slot;
113 : }
114 505 : node->recursing = true;
115 : }
116 :
117 : /* 2. Execute recursive term */
118 : for (;;)
119 : {
120 28868 : slot = ExecProcNode(innerPlan);
121 28868 : if (TupIsNull(slot))
122 3284 : {
123 : Tuplestorestate *swaptemp;
124 :
125 : /* Done if there's nothing in the intermediate table */
126 3768 : if (node->intermediate_empty)
127 484 : break;
128 :
129 : /*
130 : * Now we let the intermediate table become the work table. We
131 : * need a fresh intermediate table, so delete the tuples from the
132 : * current working table and use that as the new intermediate
133 : * table. This saves a round of free/malloc from creating a new
134 : * tuple store.
135 : */
136 3284 : tuplestore_clear(node->working_table);
137 :
138 3284 : swaptemp = node->working_table;
139 3284 : node->working_table = node->intermediate_table;
140 3284 : node->intermediate_table = swaptemp;
141 :
142 : /* mark the intermediate table as empty */
143 3284 : node->intermediate_empty = true;
144 :
145 : /* reset the recursive term */
146 3284 : innerPlan->chgParam = bms_add_member(innerPlan->chgParam,
147 : plan->wtParam);
148 :
149 : /* and continue fetching from recursive term */
150 3284 : continue;
151 : }
152 :
153 25100 : if (plan->numCols > 0)
154 : {
155 : /* Find or build hashtable entry for this tuple's group */
156 462 : LookupTupleHashEntry(node->hashtable, slot, &isnew, NULL);
157 : /* Must reset temp context after each hashtable lookup */
158 462 : MemoryContextReset(node->tempContext);
159 : /* Ignore tuple if already seen */
160 462 : if (!isnew)
161 39 : continue;
162 : }
163 :
164 : /* Else, tuple is good; stash it in intermediate table ... */
165 25061 : node->intermediate_empty = false;
166 25061 : tuplestore_puttupleslot(node->intermediate_table, slot);
167 : /* ... and return it */
168 25061 : return slot;
169 : }
170 :
171 484 : return NULL;
172 : }
173 :
174 : /* ----------------------------------------------------------------
175 : * ExecInitRecursiveUnion
176 : * ----------------------------------------------------------------
177 : */
178 : RecursiveUnionState *
179 529 : ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
180 : {
181 : RecursiveUnionState *rustate;
182 : ParamExecData *prmdata;
183 :
184 : /* check for unsupported flags */
185 : Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
186 :
187 : /*
188 : * create state structure
189 : */
190 529 : rustate = makeNode(RecursiveUnionState);
191 529 : rustate->ps.plan = (Plan *) node;
192 529 : rustate->ps.state = estate;
193 529 : rustate->ps.ExecProcNode = ExecRecursiveUnion;
194 :
195 529 : rustate->eqfuncoids = NULL;
196 529 : rustate->hashfunctions = NULL;
197 529 : rustate->hashtable = NULL;
198 529 : rustate->tempContext = NULL;
199 529 : rustate->tuplesContext = NULL;
200 :
201 : /* initialize processing state */
202 529 : rustate->recursing = false;
203 529 : rustate->intermediate_empty = true;
204 529 : rustate->working_table = tuplestore_begin_heap(false, false, work_mem);
205 529 : rustate->intermediate_table = tuplestore_begin_heap(false, false, work_mem);
206 :
207 : /*
208 : * If hashing, we need a per-tuple memory context for comparisons, and a
209 : * longer-lived context to store the hash table. The table can't just be
210 : * kept in the per-query context because we want to be able to throw it
211 : * away when rescanning. We can use a BumpContext to save storage,
212 : * because we will have no need to delete individual table entries.
213 : */
214 529 : if (node->numCols > 0)
215 : {
216 251 : rustate->tempContext =
217 251 : AllocSetContextCreate(CurrentMemoryContext,
218 : "RecursiveUnion",
219 : ALLOCSET_DEFAULT_SIZES);
220 251 : rustate->tuplesContext =
221 251 : BumpContextCreate(CurrentMemoryContext,
222 : "RecursiveUnion hashed tuples",
223 : ALLOCSET_DEFAULT_SIZES);
224 : }
225 :
226 : /*
227 : * Make the state structure available to descendant WorkTableScan nodes
228 : * via the Param slot reserved for it.
229 : */
230 529 : prmdata = &(estate->es_param_exec_vals[node->wtParam]);
231 : Assert(prmdata->execPlan == NULL);
232 529 : prmdata->value = PointerGetDatum(rustate);
233 529 : prmdata->isnull = false;
234 :
235 : /*
236 : * Miscellaneous initialization
237 : *
238 : * RecursiveUnion plans don't have expression contexts because they never
239 : * call ExecQual or ExecProject.
240 : */
241 : Assert(node->plan.qual == NIL);
242 :
243 : /*
244 : * RecursiveUnion nodes still have Result slots, which hold pointers to
245 : * tuples, so we have to initialize them.
246 : */
247 529 : ExecInitResultTypeTL(&rustate->ps);
248 :
249 : /*
250 : * Initialize result tuple type. (Note: we have to set up the result type
251 : * before initializing child nodes, because nodeWorktablescan.c expects it
252 : * to be valid.)
253 : */
254 529 : rustate->ps.ps_ProjInfo = NULL;
255 :
256 : /*
257 : * initialize child nodes
258 : */
259 529 : outerPlanState(rustate) = ExecInitNode(outerPlan(node), estate, eflags);
260 529 : innerPlanState(rustate) = ExecInitNode(innerPlan(node), estate, eflags);
261 :
262 : /*
263 : * If hashing, precompute fmgr lookup data for inner loop, and create the
264 : * hash table.
265 : */
266 529 : if (node->numCols > 0)
267 : {
268 251 : execTuplesHashPrepare(node->numCols,
269 251 : node->dupOperators,
270 : &rustate->eqfuncoids,
271 : &rustate->hashfunctions);
272 251 : build_hash_table(rustate);
273 : }
274 :
275 529 : return rustate;
276 : }
277 :
278 : /* ----------------------------------------------------------------
279 : * ExecEndRecursiveUnion
280 : *
281 : * frees any storage allocated through C routines.
282 : * ----------------------------------------------------------------
283 : */
284 : void
285 529 : ExecEndRecursiveUnion(RecursiveUnionState *node)
286 : {
287 : /* Release tuplestores */
288 529 : tuplestore_end(node->working_table);
289 529 : tuplestore_end(node->intermediate_table);
290 :
291 : /* free subsidiary stuff including hashtable data */
292 529 : if (node->tempContext)
293 251 : MemoryContextDelete(node->tempContext);
294 529 : if (node->tuplesContext)
295 251 : MemoryContextDelete(node->tuplesContext);
296 :
297 : /*
298 : * close down subplans
299 : */
300 529 : ExecEndNode(outerPlanState(node));
301 529 : ExecEndNode(innerPlanState(node));
302 529 : }
303 :
304 : /* ----------------------------------------------------------------
305 : * ExecReScanRecursiveUnion
306 : *
307 : * Rescans the relation.
308 : * ----------------------------------------------------------------
309 : */
310 : void
311 6 : ExecReScanRecursiveUnion(RecursiveUnionState *node)
312 : {
313 6 : PlanState *outerPlan = outerPlanState(node);
314 6 : PlanState *innerPlan = innerPlanState(node);
315 6 : RecursiveUnion *plan = (RecursiveUnion *) node->ps.plan;
316 :
317 : /*
318 : * Set recursive term's chgParam to tell it that we'll modify the working
319 : * table and therefore it has to rescan.
320 : */
321 6 : innerPlan->chgParam = bms_add_member(innerPlan->chgParam, plan->wtParam);
322 :
323 : /*
324 : * if chgParam of subnode is not null then plan will be re-scanned by
325 : * first ExecProcNode. Because of above, we only have to do this to the
326 : * non-recursive term.
327 : */
328 6 : if (outerPlan->chgParam == NULL)
329 0 : ExecReScan(outerPlan);
330 :
331 : /* Empty hashtable if needed */
332 6 : if (plan->numCols > 0)
333 6 : ResetTupleHashTable(node->hashtable);
334 :
335 : /* reset processing state */
336 6 : node->recursing = false;
337 6 : node->intermediate_empty = true;
338 6 : tuplestore_clear(node->working_table);
339 6 : tuplestore_clear(node->intermediate_table);
340 6 : }
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