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Previously, we cached domain constraints for the life of a query, or really for the life of the FmgrInfo struct that was used to invoke domain_in() or domain_check(). But plpgsql (and probably other places) are set up to cache such FmgrInfos for the whole lifespan of a session, which meant they could be enforcing really stale sets of constraints. On the other hand, searching pg_constraint once per query gets kind of expensive too: testing says that as much as half the runtime of a trivial query such as "SELECT 0::domaintype" went into that. To fix this, delegate the responsibility for tracking a domain's constraints to the typcache, which has the infrastructure needed to detect syscache invalidation events that signal possible changes. This not only removes unnecessary repeat reads of pg_constraint, but ensures that we never apply stale constraint data: whatever we use is the current data according to syscache rules. Unfortunately, the current configuration of the system catalogs means we have to flush cached domain-constraint data whenever either pg_type or pg_constraint changes, which happens rather a lot (eg, creation or deletion of a temp table will do it). It might be worth rearranging things to split pg_constraint into two catalogs, of which the domain constraint one would probably be very low-traffic. That's a job for another patch though, and in any case this patch should improve matters materially even with that handicap. This patch makes use of the recently-added memory context reset callback feature to manage the lifespan of domain constraint caches, so that we don't risk deleting a cache that might be in the midst of evaluation. Although this is a bug fix as well as a performance improvement, no back-patch. There haven't been many if any field complaints about stale domain constraint checks, so it doesn't seem worth taking the risk of modifying data structures as basic as MemoryContexts in back branches.
162 lines
5.6 KiB
C
162 lines
5.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* typcache.h
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* Type cache definitions.
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*
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* The type cache exists to speed lookup of certain information about data
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* types that is not directly available from a type's pg_type row.
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*
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* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/typcache.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef TYPCACHE_H
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#define TYPCACHE_H
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#include "access/tupdesc.h"
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#include "fmgr.h"
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/* DomainConstraintCache is an opaque struct known only within typcache.c */
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typedef struct DomainConstraintCache DomainConstraintCache;
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/* TypeCacheEnumData is an opaque struct known only within typcache.c */
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struct TypeCacheEnumData;
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typedef struct TypeCacheEntry
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{
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/* typeId is the hash lookup key and MUST BE FIRST */
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Oid type_id; /* OID of the data type */
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/* some subsidiary information copied from the pg_type row */
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int16 typlen;
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bool typbyval;
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char typalign;
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char typstorage;
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char typtype;
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Oid typrelid;
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/*
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* Information obtained from opfamily entries
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*
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* These will be InvalidOid if no match could be found, or if the
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* information hasn't yet been requested. Also note that for array and
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* composite types, typcache.c checks that the contained types are
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* comparable or hashable before allowing eq_opr etc to become set.
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*/
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Oid btree_opf; /* the default btree opclass' family */
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Oid btree_opintype; /* the default btree opclass' opcintype */
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Oid hash_opf; /* the default hash opclass' family */
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Oid hash_opintype; /* the default hash opclass' opcintype */
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Oid eq_opr; /* the equality operator */
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Oid lt_opr; /* the less-than operator */
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Oid gt_opr; /* the greater-than operator */
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Oid cmp_proc; /* the btree comparison function */
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Oid hash_proc; /* the hash calculation function */
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/*
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* Pre-set-up fmgr call info for the equality operator, the btree
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* comparison function, and the hash calculation function. These are kept
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* in the type cache to avoid problems with memory leaks in repeated calls
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* to functions such as array_eq, array_cmp, hash_array. There is not
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* currently a need to maintain call info for the lt_opr or gt_opr.
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*/
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FmgrInfo eq_opr_finfo;
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FmgrInfo cmp_proc_finfo;
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FmgrInfo hash_proc_finfo;
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/*
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* Tuple descriptor if it's a composite type (row type). NULL if not
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* composite or information hasn't yet been requested. (NOTE: this is a
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* reference-counted tupledesc.)
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*/
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TupleDesc tupDesc;
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/*
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* Fields computed when TYPECACHE_RANGE_INFO is requested. Zeroes if not
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* a range type or information hasn't yet been requested. Note that
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* rng_cmp_proc_finfo could be different from the element type's default
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* btree comparison function.
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*/
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struct TypeCacheEntry *rngelemtype; /* range's element type */
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Oid rng_collation; /* collation for comparisons, if any */
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FmgrInfo rng_cmp_proc_finfo; /* comparison function */
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FmgrInfo rng_canonical_finfo; /* canonicalization function, if any */
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FmgrInfo rng_subdiff_finfo; /* difference function, if any */
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/*
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* Domain constraint data if it's a domain type. NULL if not domain, or
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* if domain has no constraints, or if information hasn't been requested.
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*/
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DomainConstraintCache *domainData;
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/* Private data, for internal use of typcache.c only */
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int flags; /* flags about what we've computed */
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/*
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* Private information about an enum type. NULL if not enum or
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* information hasn't been requested.
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*/
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struct TypeCacheEnumData *enumData;
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/* We also maintain a list of all known domain-type cache entries */
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struct TypeCacheEntry *nextDomain;
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} TypeCacheEntry;
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/* Bit flags to indicate which fields a given caller needs to have set */
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#define TYPECACHE_EQ_OPR 0x0001
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#define TYPECACHE_LT_OPR 0x0002
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#define TYPECACHE_GT_OPR 0x0004
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#define TYPECACHE_CMP_PROC 0x0008
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#define TYPECACHE_HASH_PROC 0x0010
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#define TYPECACHE_EQ_OPR_FINFO 0x0020
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#define TYPECACHE_CMP_PROC_FINFO 0x0040
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#define TYPECACHE_HASH_PROC_FINFO 0x0080
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#define TYPECACHE_TUPDESC 0x0100
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#define TYPECACHE_BTREE_OPFAMILY 0x0200
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#define TYPECACHE_HASH_OPFAMILY 0x0400
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#define TYPECACHE_RANGE_INFO 0x0800
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#define TYPECACHE_DOMAIN_INFO 0x1000
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/*
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* Callers wishing to maintain a long-lived reference to a domain's constraint
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* set must store it in one of these. Use InitDomainConstraintRef() and
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* UpdateDomainConstraintRef() to manage it. Note: DomainConstraintState is
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* considered an executable expression type, so it's defined in execnodes.h.
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*/
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typedef struct DomainConstraintRef
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{
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List *constraints; /* list of DomainConstraintState nodes */
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/* Management data --- treat these fields as private to typcache.c */
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TypeCacheEntry *tcache; /* owning typcache entry */
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DomainConstraintCache *dcc; /* current constraints, or NULL if none */
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MemoryContextCallback callback; /* used to release refcount when done */
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} DomainConstraintRef;
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extern TypeCacheEntry *lookup_type_cache(Oid type_id, int flags);
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extern void InitDomainConstraintRef(Oid type_id, DomainConstraintRef *ref,
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MemoryContext refctx);
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extern void UpdateDomainConstraintRef(DomainConstraintRef *ref);
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extern bool DomainHasConstraints(Oid type_id);
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extern TupleDesc lookup_rowtype_tupdesc(Oid type_id, int32 typmod);
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extern TupleDesc lookup_rowtype_tupdesc_noerror(Oid type_id, int32 typmod,
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bool noError);
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extern TupleDesc lookup_rowtype_tupdesc_copy(Oid type_id, int32 typmod);
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extern void assign_record_type_typmod(TupleDesc tupDesc);
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extern int compare_values_of_enum(TypeCacheEntry *tcache, Oid arg1, Oid arg2);
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#endif /* TYPCACHE_H */
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