Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * attoptcache.c
4 : * Attribute options cache management.
5 : *
6 : * Attribute options are cached separately from the fixed-size portion of
7 : * pg_attribute entries, which are handled by the relcache.
8 : *
9 : * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
10 : * Portions Copyright (c) 1994, Regents of the University of California
11 : *
12 : * IDENTIFICATION
13 : * src/backend/utils/cache/attoptcache.c
14 : *
15 : *-------------------------------------------------------------------------
16 : */
17 : #include "postgres.h"
18 :
19 : #include "access/reloptions.h"
20 : #include "utils/attoptcache.h"
21 : #include "utils/catcache.h"
22 : #include "utils/hsearch.h"
23 : #include "utils/inval.h"
24 : #include "utils/syscache.h"
25 :
26 :
27 : /* Hash table for informations about each attribute's options */
28 : static HTAB *AttoptCacheHash = NULL;
29 :
30 : /* attrelid and attnum form the lookup key, and must appear first */
31 : typedef struct
32 : {
33 : Oid attrelid;
34 : int attnum;
35 : } AttoptCacheKey;
36 :
37 : typedef struct
38 : {
39 : AttoptCacheKey key; /* lookup key - must be first */
40 : AttributeOpts *opts; /* options, or NULL if none */
41 : } AttoptCacheEntry;
42 :
43 :
44 : /*
45 : * InvalidateAttoptCacheCallback
46 : * Flush all cache entries when pg_attribute is updated.
47 : *
48 : * When pg_attribute is updated, we must flush the cache entry at least
49 : * for that attribute. Currently, we just flush them all. Since attribute
50 : * options are not currently used in performance-critical paths (such as
51 : * query execution), this seems OK.
52 : */
53 : static void
54 19054 : InvalidateAttoptCacheCallback(Datum arg, int cacheid, uint32 hashvalue)
55 : {
56 : HASH_SEQ_STATUS status;
57 : AttoptCacheEntry *attopt;
58 :
59 19054 : hash_seq_init(&status, AttoptCacheHash);
60 19054 : while ((attopt = (AttoptCacheEntry *) hash_seq_search(&status)) != NULL)
61 : {
62 561 : if (attopt->opts)
63 0 : pfree(attopt->opts);
64 561 : if (hash_search(AttoptCacheHash,
65 561 : (void *) &attopt->key,
66 : HASH_REMOVE,
67 : NULL) == NULL)
68 0 : elog(ERROR, "hash table corrupted");
69 : }
70 19054 : }
71 :
72 : /*
73 : * InitializeAttoptCache
74 : * Initialize the attribute options cache.
75 : */
76 : static void
77 23 : InitializeAttoptCache(void)
78 : {
79 : HASHCTL ctl;
80 :
81 : /* Initialize the hash table. */
82 23 : MemSet(&ctl, 0, sizeof(ctl));
83 23 : ctl.keysize = sizeof(AttoptCacheKey);
84 23 : ctl.entrysize = sizeof(AttoptCacheEntry);
85 23 : AttoptCacheHash =
86 23 : hash_create("Attopt cache", 256, &ctl,
87 : HASH_ELEM | HASH_BLOBS);
88 :
89 : /* Make sure we've initialized CacheMemoryContext. */
90 23 : if (!CacheMemoryContext)
91 0 : CreateCacheMemoryContext();
92 :
93 : /* Watch for invalidation events. */
94 23 : CacheRegisterSyscacheCallback(ATTNUM,
95 : InvalidateAttoptCacheCallback,
96 : (Datum) 0);
97 23 : }
98 :
99 : /*
100 : * get_attribute_options
101 : * Fetch attribute options for a specified table OID.
102 : */
103 : AttributeOpts *
104 1060 : get_attribute_options(Oid attrelid, int attnum)
105 : {
106 : AttoptCacheKey key;
107 : AttoptCacheEntry *attopt;
108 : AttributeOpts *result;
109 : HeapTuple tp;
110 :
111 : /* Find existing cache entry, if any. */
112 1060 : if (!AttoptCacheHash)
113 23 : InitializeAttoptCache();
114 1060 : memset(&key, 0, sizeof(key)); /* make sure any padding bits are unset */
115 1060 : key.attrelid = attrelid;
116 1060 : key.attnum = attnum;
117 1060 : attopt =
118 1060 : (AttoptCacheEntry *) hash_search(AttoptCacheHash,
119 : (void *) &key,
120 : HASH_FIND,
121 : NULL);
122 :
123 : /* Not found in Attopt cache. Construct new cache entry. */
124 1060 : if (!attopt)
125 : {
126 : AttributeOpts *opts;
127 :
128 1008 : tp = SearchSysCache2(ATTNUM,
129 : ObjectIdGetDatum(attrelid),
130 : Int16GetDatum(attnum));
131 :
132 : /*
133 : * If we don't find a valid HeapTuple, it must mean someone has
134 : * managed to request attribute details for a non-existent attribute.
135 : * We treat that case as if no options were specified.
136 : */
137 1008 : if (!HeapTupleIsValid(tp))
138 0 : opts = NULL;
139 : else
140 : {
141 : Datum datum;
142 : bool isNull;
143 :
144 1008 : datum = SysCacheGetAttr(ATTNUM,
145 : tp,
146 : Anum_pg_attribute_attoptions,
147 : &isNull);
148 1008 : if (isNull)
149 1008 : opts = NULL;
150 : else
151 : {
152 0 : bytea *bytea_opts = attribute_reloptions(datum, false);
153 :
154 0 : opts = MemoryContextAlloc(CacheMemoryContext,
155 0 : VARSIZE(bytea_opts));
156 0 : memcpy(opts, bytea_opts, VARSIZE(bytea_opts));
157 : }
158 1008 : ReleaseSysCache(tp);
159 : }
160 :
161 : /*
162 : * It's important to create the actual cache entry only after reading
163 : * pg_attribute, since the read could cause a cache flush.
164 : */
165 1008 : attopt = (AttoptCacheEntry *) hash_search(AttoptCacheHash,
166 : (void *) &key,
167 : HASH_ENTER,
168 : NULL);
169 1008 : attopt->opts = opts;
170 : }
171 :
172 : /* Return results in caller's memory context. */
173 1060 : if (attopt->opts == NULL)
174 1060 : return NULL;
175 0 : result = palloc(VARSIZE(attopt->opts));
176 0 : memcpy(result, attopt->opts, VARSIZE(attopt->opts));
177 0 : return result;
178 : }
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