Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * evtcache.c
4 : * Special-purpose cache for event trigger data.
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/utils/cache/evtcache.c
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 : #include "postgres.h"
15 :
16 : #include "access/genam.h"
17 : #include "access/htup_details.h"
18 : #include "access/relation.h"
19 : #include "catalog/pg_event_trigger.h"
20 : #include "catalog/pg_type.h"
21 : #include "commands/trigger.h"
22 : #include "tcop/cmdtag.h"
23 : #include "utils/array.h"
24 : #include "utils/builtins.h"
25 : #include "utils/catcache.h"
26 : #include "utils/evtcache.h"
27 : #include "utils/hsearch.h"
28 : #include "utils/inval.h"
29 : #include "utils/memutils.h"
30 : #include "utils/rel.h"
31 : #include "utils/syscache.h"
32 :
33 : typedef enum
34 : {
35 : ETCS_NEEDS_REBUILD,
36 : ETCS_REBUILD_STARTED,
37 : ETCS_VALID,
38 : } EventTriggerCacheStateType;
39 :
40 : typedef struct
41 : {
42 : EventTriggerEvent event;
43 : List *triggerlist;
44 : } EventTriggerCacheEntry;
45 :
46 : static HTAB *EventTriggerCache;
47 : static MemoryContext EventTriggerCacheContext;
48 : static EventTriggerCacheStateType EventTriggerCacheState = ETCS_NEEDS_REBUILD;
49 :
50 : static void BuildEventTriggerCache(void);
51 : static void InvalidateEventCacheCallback(Datum arg,
52 : SysCacheIdentifier cacheid,
53 : uint32 hashvalue);
54 : static Bitmapset *DecodeTextArrayToBitmapset(Datum array);
55 :
56 : /*
57 : * Search the event cache by trigger event.
58 : *
59 : * Note that the caller had better copy any data it wants to keep around
60 : * across any operation that might touch a system catalog into some other
61 : * memory context, since a cache reset could blow the return value away.
62 : */
63 : List *
64 481619 : EventCacheLookup(EventTriggerEvent event)
65 : {
66 : EventTriggerCacheEntry *entry;
67 :
68 481619 : if (EventTriggerCacheState != ETCS_VALID)
69 3621 : BuildEventTriggerCache();
70 481619 : entry = hash_search(EventTriggerCache, &event, HASH_FIND, NULL);
71 481619 : return entry != NULL ? entry->triggerlist : NIL;
72 : }
73 :
74 : /*
75 : * Rebuild the event trigger cache.
76 : */
77 : static void
78 3621 : BuildEventTriggerCache(void)
79 : {
80 : HASHCTL ctl;
81 : HTAB *cache;
82 : Relation rel;
83 : Relation irel;
84 : SysScanDesc scan;
85 :
86 3621 : if (EventTriggerCacheContext != NULL)
87 : {
88 : /*
89 : * Free up any memory already allocated in EventTriggerCacheContext.
90 : * This can happen either because a previous rebuild failed, or
91 : * because an invalidation happened before the rebuild was complete.
92 : */
93 361 : MemoryContextReset(EventTriggerCacheContext);
94 : }
95 : else
96 : {
97 : /*
98 : * This is our first time attempting to build the cache, so we need to
99 : * set up the memory context and register a syscache callback to
100 : * capture future invalidation events.
101 : */
102 3260 : if (CacheMemoryContext == NULL)
103 0 : CreateCacheMemoryContext();
104 3260 : EventTriggerCacheContext =
105 3260 : AllocSetContextCreate(CacheMemoryContext,
106 : "EventTriggerCache",
107 : ALLOCSET_DEFAULT_SIZES);
108 3260 : CacheRegisterSyscacheCallback(EVENTTRIGGEROID,
109 : InvalidateEventCacheCallback,
110 : (Datum) 0);
111 : }
112 :
113 : /* Prevent the memory context from being nuked while we're rebuilding. */
114 3621 : EventTriggerCacheState = ETCS_REBUILD_STARTED;
115 :
116 : /* Create new hash table. */
117 3621 : ctl.keysize = sizeof(EventTriggerEvent);
118 3621 : ctl.entrysize = sizeof(EventTriggerCacheEntry);
119 3621 : ctl.hcxt = EventTriggerCacheContext;
120 3621 : cache = hash_create("EventTriggerCacheHash", 32, &ctl,
121 : HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
122 :
123 : /*
124 : * Prepare to scan pg_event_trigger in name order.
125 : */
126 3621 : rel = relation_open(EventTriggerRelationId, AccessShareLock);
127 3621 : irel = index_open(EventTriggerNameIndexId, AccessShareLock);
128 3621 : scan = systable_beginscan_ordered(rel, irel, NULL, 0, NULL);
129 :
130 : /*
131 : * Build a cache item for each pg_event_trigger tuple, and append each one
132 : * to the appropriate cache entry.
133 : */
134 : for (;;)
135 354 : {
136 : HeapTuple tup;
137 : Form_pg_event_trigger form;
138 : char *evtevent;
139 : EventTriggerEvent event;
140 : EventTriggerCacheItem *item;
141 : Datum evttags;
142 : bool evttags_isnull;
143 : EventTriggerCacheEntry *entry;
144 : bool found;
145 : MemoryContext oldcontext;
146 :
147 : /* Get next tuple. */
148 3975 : tup = systable_getnext_ordered(scan, ForwardScanDirection);
149 3975 : if (!HeapTupleIsValid(tup))
150 3621 : break;
151 :
152 : /* Skip trigger if disabled. */
153 354 : form = (Form_pg_event_trigger) GETSTRUCT(tup);
154 354 : if (form->evtenabled == TRIGGER_DISABLED)
155 17 : continue;
156 :
157 : /* Decode event name. */
158 337 : evtevent = NameStr(form->evtevent);
159 337 : if (strcmp(evtevent, "ddl_command_start") == 0)
160 44 : event = EVT_DDLCommandStart;
161 293 : else if (strcmp(evtevent, "ddl_command_end") == 0)
162 87 : event = EVT_DDLCommandEnd;
163 206 : else if (strcmp(evtevent, "sql_drop") == 0)
164 61 : event = EVT_SQLDrop;
165 145 : else if (strcmp(evtevent, "table_rewrite") == 0)
166 8 : event = EVT_TableRewrite;
167 137 : else if (strcmp(evtevent, "login") == 0)
168 137 : event = EVT_Login;
169 : else
170 0 : continue;
171 :
172 : /* Switch to correct memory context. */
173 337 : oldcontext = MemoryContextSwitchTo(EventTriggerCacheContext);
174 :
175 : /* Allocate new cache item. */
176 337 : item = palloc0_object(EventTriggerCacheItem);
177 337 : item->fnoid = form->evtfoid;
178 337 : item->enabled = form->evtenabled;
179 :
180 : /* Decode and sort tags array. */
181 337 : evttags = heap_getattr(tup, Anum_pg_event_trigger_evttags,
182 : RelationGetDescr(rel), &evttags_isnull);
183 337 : if (!evttags_isnull)
184 93 : item->tagset = DecodeTextArrayToBitmapset(evttags);
185 :
186 : /* Add to cache entry. */
187 337 : entry = hash_search(cache, &event, HASH_ENTER, &found);
188 337 : if (found)
189 21 : entry->triggerlist = lappend(entry->triggerlist, item);
190 : else
191 316 : entry->triggerlist = list_make1(item);
192 :
193 : /* Restore previous memory context. */
194 337 : MemoryContextSwitchTo(oldcontext);
195 : }
196 :
197 : /* Done with pg_event_trigger scan. */
198 3621 : systable_endscan_ordered(scan);
199 3621 : index_close(irel, AccessShareLock);
200 3621 : relation_close(rel, AccessShareLock);
201 :
202 : /* Install new cache. */
203 3621 : EventTriggerCache = cache;
204 :
205 : /*
206 : * If the cache has been invalidated since we entered this routine, we
207 : * still use and return the cache we just finished constructing, to avoid
208 : * infinite loops, but we leave the cache marked stale so that we'll
209 : * rebuild it again on next access. Otherwise, we mark the cache valid.
210 : */
211 3621 : if (EventTriggerCacheState == ETCS_REBUILD_STARTED)
212 3621 : EventTriggerCacheState = ETCS_VALID;
213 3621 : }
214 :
215 : /*
216 : * Decode text[] to a Bitmapset of CommandTags.
217 : *
218 : * We could avoid a bit of overhead here if we were willing to duplicate some
219 : * of the logic from deconstruct_array, but it doesn't seem worth the code
220 : * complexity.
221 : */
222 : static Bitmapset *
223 93 : DecodeTextArrayToBitmapset(Datum array)
224 : {
225 93 : ArrayType *arr = DatumGetArrayTypeP(array);
226 : Datum *elems;
227 : Bitmapset *bms;
228 : int i;
229 : int nelems;
230 :
231 93 : if (ARR_NDIM(arr) != 1 || ARR_HASNULL(arr) || ARR_ELEMTYPE(arr) != TEXTOID)
232 0 : elog(ERROR, "expected 1-D text array");
233 93 : deconstruct_array_builtin(arr, TEXTOID, &elems, NULL, &nelems);
234 :
235 237 : for (bms = NULL, i = 0; i < nelems; ++i)
236 : {
237 144 : char *str = TextDatumGetCString(elems[i]);
238 :
239 144 : bms = bms_add_member(bms, GetCommandTagEnum(str));
240 144 : pfree(str);
241 : }
242 :
243 93 : pfree(elems);
244 93 : if (arr != DatumGetPointer(array))
245 93 : pfree(arr);
246 :
247 93 : return bms;
248 : }
249 :
250 : /*
251 : * Flush all cache entries when pg_event_trigger is updated.
252 : *
253 : * This should be rare enough that we don't need to be very granular about
254 : * it, so we just blow away everything, which also avoids the possibility of
255 : * memory leaks.
256 : */
257 : static void
258 804 : InvalidateEventCacheCallback(Datum arg, SysCacheIdentifier cacheid,
259 : uint32 hashvalue)
260 : {
261 : /*
262 : * If the cache isn't valid, then there might be a rebuild in progress, so
263 : * we can't immediately blow it away. But it's advantageous to do this
264 : * when possible, so as to immediately free memory.
265 : */
266 804 : if (EventTriggerCacheState == ETCS_VALID)
267 : {
268 387 : MemoryContextReset(EventTriggerCacheContext);
269 387 : EventTriggerCache = NULL;
270 : }
271 :
272 : /* Mark cache for rebuild. */
273 804 : EventTriggerCacheState = ETCS_NEEDS_REBUILD;
274 804 : }
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