Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * tcn.c
4 : * triggered change notification support for PostgreSQL
5 : *
6 : * Portions Copyright (c) 2011-2025, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * contrib/tcn/tcn.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 :
16 : #include "postgres.h"
17 :
18 : #include "access/htup_details.h"
19 : #include "commands/async.h"
20 : #include "commands/trigger.h"
21 : #include "executor/spi.h"
22 : #include "lib/stringinfo.h"
23 : #include "utils/rel.h"
24 : #include "utils/syscache.h"
25 :
26 4 : PG_MODULE_MAGIC_EXT(
27 : .name = "tcn",
28 : .version = PG_VERSION
29 : );
30 :
31 : /*
32 : * Copy from s (for source) to r (for result), wrapping with q (quote)
33 : * characters and doubling any quote characters found.
34 : */
35 : static void
36 30 : strcpy_quoted(StringInfo r, const char *s, const char q)
37 : {
38 30 : appendStringInfoCharMacro(r, q);
39 140 : while (*s)
40 : {
41 110 : if (*s == q)
42 0 : appendStringInfoCharMacro(r, q);
43 110 : appendStringInfoCharMacro(r, *s);
44 110 : s++;
45 : }
46 30 : appendStringInfoCharMacro(r, q);
47 30 : }
48 :
49 : /*
50 : * triggered_change_notification
51 : *
52 : * This trigger function will send a notification of data modification with
53 : * primary key values. The channel will be "tcn" unless the trigger is
54 : * created with a parameter, in which case that parameter will be used.
55 : */
56 4 : PG_FUNCTION_INFO_V1(triggered_change_notification);
57 :
58 : Datum
59 10 : triggered_change_notification(PG_FUNCTION_ARGS)
60 : {
61 10 : TriggerData *trigdata = (TriggerData *) fcinfo->context;
62 : Trigger *trigger;
63 : int nargs;
64 : HeapTuple trigtuple;
65 : Relation rel;
66 : TupleDesc tupdesc;
67 : char *channel;
68 : char operation;
69 10 : StringInfo payload = makeStringInfo();
70 : bool foundPK;
71 :
72 : List *indexoidlist;
73 : ListCell *indexoidscan;
74 :
75 : /* make sure it's called as a trigger */
76 10 : if (!CALLED_AS_TRIGGER(fcinfo))
77 0 : ereport(ERROR,
78 : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
79 : errmsg("triggered_change_notification: must be called as trigger")));
80 :
81 : /* and that it's called after the change */
82 10 : if (!TRIGGER_FIRED_AFTER(trigdata->tg_event))
83 0 : ereport(ERROR,
84 : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
85 : errmsg("triggered_change_notification: must be called after the change")));
86 :
87 : /* and that it's called for each row */
88 10 : if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
89 0 : ereport(ERROR,
90 : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
91 : errmsg("triggered_change_notification: must be called for each row")));
92 :
93 10 : if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
94 4 : operation = 'I';
95 6 : else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
96 2 : operation = 'U';
97 4 : else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
98 4 : operation = 'D';
99 : else
100 : {
101 0 : elog(ERROR, "triggered_change_notification: trigger fired by unrecognized operation");
102 : operation = 'X'; /* silence compiler warning */
103 : }
104 :
105 10 : trigger = trigdata->tg_trigger;
106 10 : nargs = trigger->tgnargs;
107 10 : if (nargs > 1)
108 0 : ereport(ERROR,
109 : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
110 : errmsg("triggered_change_notification: must not be called with more than one parameter")));
111 :
112 10 : if (nargs == 0)
113 0 : channel = "tcn";
114 : else
115 10 : channel = trigger->tgargs[0];
116 :
117 : /* get tuple data */
118 10 : trigtuple = trigdata->tg_trigtuple;
119 10 : rel = trigdata->tg_relation;
120 10 : tupdesc = rel->rd_att;
121 :
122 10 : foundPK = false;
123 :
124 : /*
125 : * Get the list of index OIDs for the table from the relcache, and look up
126 : * each one in the pg_index syscache until we find one marked primary key
127 : * (hopefully there isn't more than one such).
128 : */
129 10 : indexoidlist = RelationGetIndexList(rel);
130 :
131 10 : foreach(indexoidscan, indexoidlist)
132 : {
133 10 : Oid indexoid = lfirst_oid(indexoidscan);
134 : HeapTuple indexTuple;
135 : Form_pg_index index;
136 :
137 10 : indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
138 10 : if (!HeapTupleIsValid(indexTuple)) /* should not happen */
139 0 : elog(ERROR, "cache lookup failed for index %u", indexoid);
140 10 : index = (Form_pg_index) GETSTRUCT(indexTuple);
141 : /* we're only interested if it is the primary key and valid */
142 10 : if (index->indisprimary && index->indisvalid)
143 : {
144 10 : int indnkeyatts = index->indnkeyatts;
145 :
146 10 : if (indnkeyatts > 0)
147 : {
148 : int i;
149 :
150 10 : foundPK = true;
151 :
152 10 : strcpy_quoted(payload, RelationGetRelationName(rel), '"');
153 10 : appendStringInfoCharMacro(payload, ',');
154 10 : appendStringInfoCharMacro(payload, operation);
155 :
156 20 : for (i = 0; i < indnkeyatts; i++)
157 : {
158 10 : int colno = index->indkey.values[i];
159 10 : Form_pg_attribute attr = TupleDescAttr(tupdesc, colno - 1);
160 :
161 10 : appendStringInfoCharMacro(payload, ',');
162 10 : strcpy_quoted(payload, NameStr(attr->attname), '"');
163 10 : appendStringInfoCharMacro(payload, '=');
164 10 : strcpy_quoted(payload, SPI_getvalue(trigtuple, tupdesc, colno), '\'');
165 : }
166 :
167 10 : Async_Notify(channel, payload->data);
168 : }
169 10 : ReleaseSysCache(indexTuple);
170 10 : break;
171 : }
172 0 : ReleaseSysCache(indexTuple);
173 : }
174 :
175 10 : list_free(indexoidlist);
176 :
177 10 : if (!foundPK)
178 0 : ereport(ERROR,
179 : (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
180 : errmsg("triggered_change_notification: must be called on a table with a primary key")));
181 :
182 10 : return PointerGetDatum(NULL); /* after trigger; value doesn't matter */
183 : }
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