Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * constraint.c
4 : : * PostgreSQL CONSTRAINT support code.
5 : : *
6 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : * IDENTIFICATION
10 : : * src/backend/commands/constraint.c
11 : : *
12 : : *-------------------------------------------------------------------------
13 : : */
14 : : #include "postgres.h"
15 : :
16 : : #include "access/genam.h"
17 : : #include "access/tableam.h"
18 : : #include "catalog/index.h"
19 : : #include "commands/trigger.h"
20 : : #include "executor/executor.h"
21 : : #include "utils/fmgrprotos.h"
22 : : #include "utils/snapmgr.h"
23 : :
24 : :
25 : : /*
26 : : * unique_key_recheck - trigger function to do a deferred uniqueness check.
27 : : *
28 : : * This now also does deferred exclusion-constraint checks, so the name is
29 : : * somewhat historical.
30 : : *
31 : : * This is invoked as an AFTER ROW trigger for both INSERT and UPDATE,
32 : : * for any rows recorded as potentially violating a deferrable unique
33 : : * or exclusion constraint.
34 : : *
35 : : * This may be an end-of-statement check, a commit-time check, or a
36 : : * check triggered by a SET CONSTRAINTS command.
37 : : */
38 : : Datum
6124 tgl@sss.pgh.pa.us 39 :CBC 81 : unique_key_recheck(PG_FUNCTION_ARGS)
40 : : {
2223 41 : 81 : TriggerData *trigdata = (TriggerData *) fcinfo->context;
6124 42 : 81 : const char *funcname = "unique_key_recheck";
43 : : ItemPointerData checktid;
44 : : ItemPointerData tmptid;
45 : : Relation indexRel;
46 : : IndexInfo *indexInfo;
47 : : EState *estate;
48 : : ExprContext *econtext;
49 : : TupleTableSlot *slot;
50 : : Datum values[INDEX_MAX_KEYS];
51 : : bool isnull[INDEX_MAX_KEYS];
52 : :
53 : : /*
54 : : * Make sure this is being called as an AFTER ROW trigger. Note:
55 : : * translatable error strings are shared with ri_triggers.c, so resist the
56 : : * temptation to fold the function name into them.
57 : : */
58 [ + - - + ]: 81 : if (!CALLED_AS_TRIGGER(fcinfo))
6124 tgl@sss.pgh.pa.us 59 [ # # ]:UBC 0 : ereport(ERROR,
60 : : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
61 : : errmsg("function \"%s\" was not called by trigger manager",
62 : : funcname)));
63 : :
6124 tgl@sss.pgh.pa.us 64 [ + - ]:CBC 81 : if (!TRIGGER_FIRED_AFTER(trigdata->tg_event) ||
65 [ - + ]: 81 : !TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
6124 tgl@sss.pgh.pa.us 66 [ # # ]:UBC 0 : ereport(ERROR,
67 : : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
68 : : errmsg("function \"%s\" must be fired AFTER ROW",
69 : : funcname)));
70 : :
71 : : /*
72 : : * Get the new data that was inserted/updated.
73 : : */
6124 tgl@sss.pgh.pa.us 74 [ + + ]:CBC 81 : if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
2612 andres@anarazel.de 75 : 57 : checktid = trigdata->tg_trigslot->tts_tid;
6124 tgl@sss.pgh.pa.us 76 [ + - ]: 24 : else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
2612 andres@anarazel.de 77 : 24 : checktid = trigdata->tg_newslot->tts_tid;
78 : : else
79 : : {
6124 tgl@sss.pgh.pa.us 80 [ # # ]:UBC 0 : ereport(ERROR,
81 : : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
82 : : errmsg("function \"%s\" must be fired for INSERT or UPDATE",
83 : : funcname)));
84 : : ItemPointerSetInvalid(&checktid); /* keep compiler quiet */
85 : : }
86 : :
2612 andres@anarazel.de 87 :CBC 81 : slot = table_slot_create(trigdata->tg_relation, NULL);
88 : :
89 : : /*
90 : : * If the row pointed at by checktid is now dead (ie, inserted and then
91 : : * deleted within our transaction), we can skip the check. However, we
92 : : * have to be careful, because this trigger gets queued only in response
93 : : * to index insertions; which means it does not get queued e.g. for HOT
94 : : * updates. The row we are called for might now be dead, but have a live
95 : : * HOT child, in which case we still need to make the check ---
96 : : * effectively, we're applying the check against the live child row,
97 : : * although we can use the values from this row since by definition all
98 : : * columns of interest to us are the same.
99 : : *
100 : : * This might look like just an optimization, because the index AM will
101 : : * make this identical test before throwing an error. But it's actually
102 : : * needed for correctness, because the index AM will also throw an error
103 : : * if it doesn't find the index entry for the row. If the row's dead then
104 : : * it's possible the index entry has also been marked dead, and even
105 : : * removed.
106 : : */
107 : 81 : tmptid = checktid;
108 : : {
36 melanieplageman@gmai 109 :GNC 81 : IndexFetchTableData *scan = table_index_fetch_begin(trigdata->tg_relation,
110 : : SO_NONE);
2540 tgl@sss.pgh.pa.us 111 :CBC 81 : bool call_again = false;
112 : :
2612 andres@anarazel.de 113 [ - + ]: 81 : if (!table_index_fetch_tuple(scan, &tmptid, SnapshotSelf, slot,
114 : : &call_again, NULL))
115 : : {
116 : : /*
117 : : * All rows referenced by the index entry are dead, so skip the
118 : : * check.
119 : : */
2612 andres@anarazel.de 120 :UBC 0 : ExecDropSingleTupleTableSlot(slot);
121 : 0 : table_index_fetch_end(scan);
122 : 0 : return PointerGetDatum(NULL);
123 : : }
2612 andres@anarazel.de 124 :CBC 81 : table_index_fetch_end(scan);
125 : : }
126 : :
127 : : /*
128 : : * Open the index, acquiring a RowExclusiveLock, just as if we were going
129 : : * to update it. (This protects against possible changes of the index
130 : : * schema, not against concurrent updates.)
131 : : */
6124 tgl@sss.pgh.pa.us 132 : 81 : indexRel = index_open(trigdata->tg_trigger->tgconstrindid,
133 : : RowExclusiveLock);
134 : 81 : indexInfo = BuildIndexInfo(indexRel);
135 : :
136 : : /*
137 : : * Typically the index won't have expressions, but if it does we need an
138 : : * EState to evaluate them. We need it for exclusion constraints too,
139 : : * even if they are just on simple columns.
140 : : */
5993 141 [ + - ]: 81 : if (indexInfo->ii_Expressions != NIL ||
142 [ + + ]: 81 : indexInfo->ii_ExclusionOps != NULL)
143 : : {
6124 144 : 16 : estate = CreateExecutorState();
145 [ - + ]: 16 : econtext = GetPerTupleExprContext(estate);
146 : 16 : econtext->ecxt_scantuple = slot;
147 : : }
148 : : else
149 : 65 : estate = NULL;
150 : :
151 : : /*
152 : : * Form the index values and isnull flags for the index entry that we need
153 : : * to check.
154 : : *
155 : : * Note: if the index uses functions that are not as immutable as they are
156 : : * supposed to be, this could produce an index tuple different from the
157 : : * original. The index AM can catch such errors by verifying that it
158 : : * finds a matching index entry with the tuple's TID. For exclusion
159 : : * constraints we check this in check_exclusion_constraint().
160 : : */
161 : 81 : FormIndexDatum(indexInfo, slot, estate, values, isnull);
162 : :
163 : : /*
164 : : * Now do the appropriate check.
165 : : */
5993 166 [ + + ]: 81 : if (indexInfo->ii_ExclusionOps == NULL)
167 : : {
168 : : /*
169 : : * Note: this is not a real insert; it is a check that the index entry
170 : : * that has already been inserted is unique. Passing the tuple's tid
171 : : * (i.e. unmodified by table_index_fetch_tuple()) is correct even if
172 : : * the row is now dead, because that is the TID the index will know
173 : : * about.
174 : : */
2612 andres@anarazel.de 175 : 65 : index_insert(indexRel, values, isnull, &checktid,
176 : : trigdata->tg_relation, UNIQUE_CHECK_EXISTING,
177 : : false, indexInfo);
178 : :
179 : : /* Cleanup cache possibly initialized by index_insert. */
746 tomas.vondra@postgre 180 : 36 : index_insert_cleanup(indexRel, indexInfo);
181 : : }
182 : : else
183 : : {
184 : : /*
185 : : * For exclusion constraints we just do the normal check, but now it's
186 : : * okay to throw error. In the HOT-update case, we must use the live
187 : : * HOT child's TID here, else check_exclusion_constraint will think
188 : : * the child is a conflict.
189 : : */
5993 tgl@sss.pgh.pa.us 190 : 16 : check_exclusion_constraint(trigdata->tg_relation, indexRel, indexInfo,
191 : : &tmptid, values, isnull,
192 : : estate, false);
193 : : }
194 : :
195 : : /*
196 : : * If that worked, then this index entry is unique or non-excluded, and we
197 : : * are done.
198 : : */
6124 199 [ + + ]: 40 : if (estate != NULL)
200 : 4 : FreeExecutorState(estate);
201 : :
202 : 40 : ExecDropSingleTupleTableSlot(slot);
203 : :
204 : 40 : index_close(indexRel, RowExclusiveLock);
205 : :
206 : 40 : return PointerGetDatum(NULL);
207 : : }
|
