1 /*-------------------------------------------------------------------------
2  *
3  * catcache.h
4  *	  Low-level catalog cache definitions.
5  *
6  * NOTE: every catalog cache must have a corresponding unique index on
7  * the system table that it caches --- ie, the index must match the keys
8  * used to do lookups in this cache.  All cache fetches are done with
9  * indexscans (under normal conditions).  The index should be unique to
10  * guarantee that there can only be one matching row for a key combination.
11  *
12  *
13  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
14  * Portions Copyright (c) 1994, Regents of the University of California
15  *
16  * src/include/utils/catcache.h
17  *
18  *-------------------------------------------------------------------------
19  */
20 #ifndef CATCACHE_H
21 #define CATCACHE_H
22 
23 #include "access/htup.h"
24 #include "access/skey.h"
25 #include "lib/ilist.h"
26 #include "utils/relcache.h"
27 
28 /*
29  *		struct catctup:			individual tuple in the cache.
30  *		struct catclist:		list of tuples matching a partial key.
31  *		struct catcache:		information for managing a cache.
32  *		struct catcacheheader:	information for managing all the caches.
33  */
34 
35 #define CATCACHE_MAXKEYS		4
36 
37 
38 /* function computing a datum's hash */
39 typedef uint32 (*CCHashFN) (Datum datum);
40 
41 /* function computing equality of two datums */
42 typedef bool (*CCFastEqualFN) (Datum a, Datum b);
43 
44 typedef struct catcache
45 {
46 	int			id;				/* cache identifier --- see syscache.h */
47 	int			cc_nbuckets;	/* # of hash buckets in this cache */
48 	TupleDesc	cc_tupdesc;		/* tuple descriptor (copied from reldesc) */
49 	dlist_head *cc_bucket;		/* hash buckets */
50 	CCHashFN	cc_hashfunc[CATCACHE_MAXKEYS];	/* hash function for each key */
51 	CCFastEqualFN cc_fastequal[CATCACHE_MAXKEYS];	/* fast equal function for
52 													 * each key */
53 	int			cc_keyno[CATCACHE_MAXKEYS]; /* AttrNumber of each key */
54 	dlist_head	cc_lists;		/* list of CatCList structs */
55 	int			cc_ntup;		/* # of tuples currently in this cache */
56 	int			cc_nkeys;		/* # of keys (1..CATCACHE_MAXKEYS) */
57 	const char *cc_relname;		/* name of relation the tuples come from */
58 	Oid			cc_reloid;		/* OID of relation the tuples come from */
59 	Oid			cc_indexoid;	/* OID of index matching cache keys */
60 	bool		cc_relisshared; /* is relation shared across databases? */
61 	slist_node	cc_next;		/* list link */
62 	ScanKeyData cc_skey[CATCACHE_MAXKEYS];	/* precomputed key info for heap
63 											 * scans */
64 
65 	/*
66 	 * Keep these at the end, so that compiling catcache.c with CATCACHE_STATS
67 	 * doesn't break ABI for other modules
68 	 */
69 #ifdef CATCACHE_STATS
70 	long		cc_searches;	/* total # searches against this cache */
71 	long		cc_hits;		/* # of matches against existing entry */
72 	long		cc_neg_hits;	/* # of matches against negative entry */
73 	long		cc_newloads;	/* # of successful loads of new entry */
74 
75 	/*
76 	 * cc_searches - (cc_hits + cc_neg_hits + cc_newloads) is number of failed
77 	 * searches, each of which will result in loading a negative entry
78 	 */
79 	long		cc_invals;		/* # of entries invalidated from cache */
80 	long		cc_lsearches;	/* total # list-searches */
81 	long		cc_lhits;		/* # of matches against existing lists */
82 #endif
83 } CatCache;
84 
85 
86 typedef struct catctup
87 {
88 	int			ct_magic;		/* for identifying CatCTup entries */
89 #define CT_MAGIC   0x57261502
90 
91 	uint32		hash_value;		/* hash value for this tuple's keys */
92 
93 	/*
94 	 * Lookup keys for the entry. By-reference datums point into the tuple for
95 	 * positive cache entries, and are separately allocated for negative ones.
96 	 */
97 	Datum		keys[CATCACHE_MAXKEYS];
98 
99 	/*
100 	 * Each tuple in a cache is a member of a dlist that stores the elements
101 	 * of its hash bucket.  We keep each dlist in LRU order to speed repeated
102 	 * lookups.
103 	 */
104 	dlist_node	cache_elem;		/* list member of per-bucket list */
105 
106 	/*
107 	 * A tuple marked "dead" must not be returned by subsequent searches.
108 	 * However, it won't be physically deleted from the cache until its
109 	 * refcount goes to zero.  (If it's a member of a CatCList, the list's
110 	 * refcount must go to zero, too; also, remember to mark the list dead at
111 	 * the same time the tuple is marked.)
112 	 *
113 	 * A negative cache entry is an assertion that there is no tuple matching
114 	 * a particular key.  This is just as useful as a normal entry so far as
115 	 * avoiding catalog searches is concerned.  Management of positive and
116 	 * negative entries is identical.
117 	 */
118 	int			refcount;		/* number of active references */
119 	bool		dead;			/* dead but not yet removed? */
120 	bool		negative;		/* negative cache entry? */
121 	HeapTupleData tuple;		/* tuple management header */
122 
123 	/*
124 	 * The tuple may also be a member of at most one CatCList.  (If a single
125 	 * catcache is list-searched with varying numbers of keys, we may have to
126 	 * make multiple entries for the same tuple because of this restriction.
127 	 * Currently, that's not expected to be common, so we accept the potential
128 	 * inefficiency.)
129 	 */
130 	struct catclist *c_list;	/* containing CatCList, or NULL if none */
131 
132 	CatCache   *my_cache;		/* link to owning catcache */
133 	/* properly aligned tuple data follows, unless a negative entry */
134 } CatCTup;
135 
136 
137 /*
138  * A CatCList describes the result of a partial search, ie, a search using
139  * only the first K key columns of an N-key cache.  We store the keys used
140  * into the keys attribute to represent the stored key set.  The CatCList
141  * object contains links to cache entries for all the table rows satisfying
142  * the partial key.  (Note: none of these will be negative cache entries.)
143  *
144  * A CatCList is only a member of a per-cache list; we do not currently
145  * divide them into hash buckets.
146  *
147  * A list marked "dead" must not be returned by subsequent searches.
148  * However, it won't be physically deleted from the cache until its
149  * refcount goes to zero.  (A list should be marked dead if any of its
150  * member entries are dead.)
151  *
152  * If "ordered" is true then the member tuples appear in the order of the
153  * cache's underlying index.  This will be true in normal operation, but
154  * might not be true during bootstrap or recovery operations. (namespace.c
155  * is able to save some cycles when it is true.)
156  */
157 typedef struct catclist
158 {
159 	int			cl_magic;		/* for identifying CatCList entries */
160 #define CL_MAGIC   0x52765103
161 
162 	uint32		hash_value;		/* hash value for lookup keys */
163 
164 	dlist_node	cache_elem;		/* list member of per-catcache list */
165 
166 	/*
167 	 * Lookup keys for the entry, with the first nkeys elements being valid.
168 	 * All by-reference are separately allocated.
169 	 */
170 	Datum		keys[CATCACHE_MAXKEYS];
171 
172 	int			refcount;		/* number of active references */
173 	bool		dead;			/* dead but not yet removed? */
174 	bool		ordered;		/* members listed in index order? */
175 	short		nkeys;			/* number of lookup keys specified */
176 	int			n_members;		/* number of member tuples */
177 	CatCache   *my_cache;		/* link to owning catcache */
178 	CatCTup    *members[FLEXIBLE_ARRAY_MEMBER]; /* members */
179 } CatCList;
180 
181 
182 typedef struct catcacheheader
183 {
184 	slist_head	ch_caches;		/* head of list of CatCache structs */
185 	int			ch_ntup;		/* # of tuples in all caches */
186 } CatCacheHeader;
187 
188 
189 /* this extern duplicates utils/memutils.h... */
190 extern PGDLLIMPORT MemoryContext CacheMemoryContext;
191 
192 extern void CreateCacheMemoryContext(void);
193 
194 extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
195 							  int nkeys, const int *key,
196 							  int nbuckets);
197 extern void InitCatCachePhase2(CatCache *cache, bool touch_index);
198 
199 extern HeapTuple SearchCatCache(CatCache *cache,
200 								Datum v1, Datum v2, Datum v3, Datum v4);
201 extern HeapTuple SearchCatCache1(CatCache *cache,
202 								 Datum v1);
203 extern HeapTuple SearchCatCache2(CatCache *cache,
204 								 Datum v1, Datum v2);
205 extern HeapTuple SearchCatCache3(CatCache *cache,
206 								 Datum v1, Datum v2, Datum v3);
207 extern HeapTuple SearchCatCache4(CatCache *cache,
208 								 Datum v1, Datum v2, Datum v3, Datum v4);
209 extern void ReleaseCatCache(HeapTuple tuple);
210 
211 extern uint32 GetCatCacheHashValue(CatCache *cache,
212 								   Datum v1, Datum v2,
213 								   Datum v3, Datum v4);
214 
215 extern CatCList *SearchCatCacheList(CatCache *cache, int nkeys,
216 									Datum v1, Datum v2,
217 									Datum v3);
218 extern void ReleaseCatCacheList(CatCList *list);
219 
220 extern void ResetCatalogCaches(void);
221 extern void CatalogCacheFlushCatalog(Oid catId);
222 extern void CatCacheInvalidate(CatCache *cache, uint32 hashValue);
223 extern void PrepareToInvalidateCacheTuple(Relation relation,
224 										  HeapTuple tuple,
225 										  HeapTuple newtuple,
226 										  void (*function) (int, uint32, Oid));
227 
228 extern void PrintCatCacheLeakWarning(HeapTuple tuple);
229 extern void PrintCatCacheListLeakWarning(CatCList *list);
230 
231 #endif							/* CATCACHE_H */
232