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Use the typcache to cache constraints for domain types.
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.
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10 files changed

+547
-181
lines changed

10 files changed

+547
-181
lines changed

src/backend/commands/tablecmds.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -4824,7 +4824,7 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
48244824
{
48254825
defval = (Expr *) build_column_default(rel, attribute.attnum);
48264826

4827-
if (!defval && GetDomainConstraints(typeOid) != NIL)
4827+
if (!defval && DomainHasConstraints(typeOid))
48284828
{
48294829
Oid baseTypeId;
48304830
int32 baseTypeMod;
@@ -7778,7 +7778,7 @@ ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno)
77787778
{
77797779
CoerceToDomain *d = (CoerceToDomain *) expr;
77807780

7781-
if (GetDomainConstraints(d->resulttype) != NIL)
7781+
if (DomainHasConstraints(d->resulttype))
77827782
return true;
77837783
expr = (Node *) d->arg;
77847784
}

src/backend/commands/typecmds.c

Lines changed: 0 additions & 127 deletions
Original file line numberDiff line numberDiff line change
@@ -31,15 +31,11 @@
3131
*/
3232
#include "postgres.h"
3333

34-
#include "access/genam.h"
35-
#include "access/heapam.h"
3634
#include "access/htup_details.h"
3735
#include "access/xact.h"
3836
#include "catalog/binary_upgrade.h"
3937
#include "catalog/catalog.h"
40-
#include "catalog/dependency.h"
4138
#include "catalog/heap.h"
42-
#include "catalog/indexing.h"
4339
#include "catalog/objectaccess.h"
4440
#include "catalog/pg_authid.h"
4541
#include "catalog/pg_collation.h"
@@ -59,14 +55,12 @@
5955
#include "executor/executor.h"
6056
#include "miscadmin.h"
6157
#include "nodes/makefuncs.h"
62-
#include "optimizer/planner.h"
6358
#include "optimizer/var.h"
6459
#include "parser/parse_coerce.h"
6560
#include "parser/parse_collate.h"
6661
#include "parser/parse_expr.h"
6762
#include "parser/parse_func.h"
6863
#include "parser/parse_type.h"
69-
#include "utils/acl.h"
7064
#include "utils/builtins.h"
7165
#include "utils/fmgroids.h"
7266
#include "utils/lsyscache.h"
@@ -75,7 +69,6 @@
7569
#include "utils/ruleutils.h"
7670
#include "utils/snapmgr.h"
7771
#include "utils/syscache.h"
78-
#include "utils/tqual.h"
7972

8073

8174
/* result structure for get_rels_with_domain() */
@@ -3081,126 +3074,6 @@ domainAddConstraint(Oid domainOid, Oid domainNamespace, Oid baseTypeOid,
30813074
return ccbin;
30823075
}
30833076

3084-
/*
3085-
* GetDomainConstraints - get a list of the current constraints of domain
3086-
*
3087-
* Returns a possibly-empty list of DomainConstraintState nodes.
3088-
*
3089-
* This is called by the executor during plan startup for a CoerceToDomain
3090-
* expression node. The given constraints will be checked for each value
3091-
* passed through the node.
3092-
*
3093-
* We allow this to be called for non-domain types, in which case the result
3094-
* is always NIL.
3095-
*/
3096-
List *
3097-
GetDomainConstraints(Oid typeOid)
3098-
{
3099-
List *result = NIL;
3100-
bool notNull = false;
3101-
Relation conRel;
3102-
3103-
conRel = heap_open(ConstraintRelationId, AccessShareLock);
3104-
3105-
for (;;)
3106-
{
3107-
HeapTuple tup;
3108-
HeapTuple conTup;
3109-
Form_pg_type typTup;
3110-
ScanKeyData key[1];
3111-
SysScanDesc scan;
3112-
3113-
tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typeOid));
3114-
if (!HeapTupleIsValid(tup))
3115-
elog(ERROR, "cache lookup failed for type %u", typeOid);
3116-
typTup = (Form_pg_type) GETSTRUCT(tup);
3117-
3118-
if (typTup->typtype != TYPTYPE_DOMAIN)
3119-
{
3120-
/* Not a domain, so done */
3121-
ReleaseSysCache(tup);
3122-
break;
3123-
}
3124-
3125-
/* Test for NOT NULL Constraint */
3126-
if (typTup->typnotnull)
3127-
notNull = true;
3128-
3129-
/* Look for CHECK Constraints on this domain */
3130-
ScanKeyInit(&key[0],
3131-
Anum_pg_constraint_contypid,
3132-
BTEqualStrategyNumber, F_OIDEQ,
3133-
ObjectIdGetDatum(typeOid));
3134-
3135-
scan = systable_beginscan(conRel, ConstraintTypidIndexId, true,
3136-
NULL, 1, key);
3137-
3138-
while (HeapTupleIsValid(conTup = systable_getnext(scan)))
3139-
{
3140-
Form_pg_constraint c = (Form_pg_constraint) GETSTRUCT(conTup);
3141-
Datum val;
3142-
bool isNull;
3143-
Expr *check_expr;
3144-
DomainConstraintState *r;
3145-
3146-
/* Ignore non-CHECK constraints (presently, shouldn't be any) */
3147-
if (c->contype != CONSTRAINT_CHECK)
3148-
continue;
3149-
3150-
/*
3151-
* Not expecting conbin to be NULL, but we'll test for it anyway
3152-
*/
3153-
val = fastgetattr(conTup, Anum_pg_constraint_conbin,
3154-
conRel->rd_att, &isNull);
3155-
if (isNull)
3156-
elog(ERROR, "domain \"%s\" constraint \"%s\" has NULL conbin",
3157-
NameStr(typTup->typname), NameStr(c->conname));
3158-
3159-
check_expr = (Expr *) stringToNode(TextDatumGetCString(val));
3160-
3161-
/* ExecInitExpr assumes we've planned the expression */
3162-
check_expr = expression_planner(check_expr);
3163-
3164-
r = makeNode(DomainConstraintState);
3165-
r->constrainttype = DOM_CONSTRAINT_CHECK;
3166-
r->name = pstrdup(NameStr(c->conname));
3167-
r->check_expr = ExecInitExpr(check_expr, NULL);
3168-
3169-
/*
3170-
* use lcons() here because constraints of lower domains should be
3171-
* applied earlier.
3172-
*/
3173-
result = lcons(r, result);
3174-
}
3175-
3176-
systable_endscan(scan);
3177-
3178-
/* loop to next domain in stack */
3179-
typeOid = typTup->typbasetype;
3180-
ReleaseSysCache(tup);
3181-
}
3182-
3183-
heap_close(conRel, AccessShareLock);
3184-
3185-
/*
3186-
* Only need to add one NOT NULL check regardless of how many domains in
3187-
* the stack request it.
3188-
*/
3189-
if (notNull)
3190-
{
3191-
DomainConstraintState *r = makeNode(DomainConstraintState);
3192-
3193-
r->constrainttype = DOM_CONSTRAINT_NOTNULL;
3194-
r->name = pstrdup("NOT NULL");
3195-
r->check_expr = NULL;
3196-
3197-
/* lcons to apply the nullness check FIRST */
3198-
result = lcons(r, result);
3199-
}
3200-
3201-
return result;
3202-
}
3203-
32043077

32053078
/*
32063079
* Execute ALTER TYPE RENAME

src/backend/executor/execQual.c

Lines changed: 10 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -41,7 +41,6 @@
4141
#include "access/tupconvert.h"
4242
#include "catalog/objectaccess.h"
4343
#include "catalog/pg_type.h"
44-
#include "commands/typecmds.h"
4544
#include "executor/execdebug.h"
4645
#include "executor/nodeSubplan.h"
4746
#include "funcapi.h"
@@ -3929,7 +3928,10 @@ ExecEvalCoerceToDomain(CoerceToDomainState *cstate, ExprContext *econtext,
39293928
if (isDone && *isDone == ExprEndResult)
39303929
return result; /* nothing to check */
39313930

3932-
foreach(l, cstate->constraints)
3931+
/* Make sure we have up-to-date constraints */
3932+
UpdateDomainConstraintRef(cstate->constraint_ref);
3933+
3934+
foreach(l, cstate->constraint_ref->constraints)
39333935
{
39343936
DomainConstraintState *con = (DomainConstraintState *) lfirst(l);
39353937

@@ -5050,7 +5052,12 @@ ExecInitExpr(Expr *node, PlanState *parent)
50505052

50515053
cstate->xprstate.evalfunc = (ExprStateEvalFunc) ExecEvalCoerceToDomain;
50525054
cstate->arg = ExecInitExpr(ctest->arg, parent);
5053-
cstate->constraints = GetDomainConstraints(ctest->resulttype);
5055+
/* We spend an extra palloc to reduce header inclusions */
5056+
cstate->constraint_ref = (DomainConstraintRef *)
5057+
palloc(sizeof(DomainConstraintRef));
5058+
InitDomainConstraintRef(ctest->resulttype,
5059+
cstate->constraint_ref,
5060+
CurrentMemoryContext);
50545061
state = (ExprState *) cstate;
50555062
}
50565063
break;

src/backend/utils/adt/domains.c

Lines changed: 36 additions & 42 deletions
Original file line numberDiff line numberDiff line change
@@ -12,10 +12,9 @@
1212
* The overhead required for constraint checking can be high, since examining
1313
* the catalogs to discover the constraints for a given domain is not cheap.
1414
* We have three mechanisms for minimizing this cost:
15-
* 1. In a nest of domains, we flatten the checking of all the levels
16-
* into just one operation.
17-
* 2. We cache the list of constraint items in the FmgrInfo struct
18-
* passed by the caller.
15+
* 1. We rely on the typcache to keep up-to-date copies of the constraints.
16+
* 2. In a nest of domains, we flatten the checking of all the levels
17+
* into just one operation (the typcache does this for us).
1918
* 3. If there are CHECK constraints, we cache a standalone ExprContext
2019
* to evaluate them in.
2120
*
@@ -33,12 +32,12 @@
3332

3433
#include "access/htup_details.h"
3534
#include "catalog/pg_type.h"
36-
#include "commands/typecmds.h"
3735
#include "executor/executor.h"
3836
#include "lib/stringinfo.h"
3937
#include "utils/builtins.h"
4038
#include "utils/lsyscache.h"
4139
#include "utils/syscache.h"
40+
#include "utils/typcache.h"
4241

4342

4443
/*
@@ -52,8 +51,8 @@ typedef struct DomainIOData
5251
Oid typioparam;
5352
int32 typtypmod;
5453
FmgrInfo proc;
55-
/* List of constraint items to check */
56-
List *constraint_list;
54+
/* Reference to cached list of constraint items to check */
55+
DomainConstraintRef constraint_ref;
5756
/* Context for evaluating CHECK constraints in */
5857
ExprContext *econtext;
5958
/* Memory context this cache is in */
@@ -63,16 +62,19 @@ typedef struct DomainIOData
6362

6463
/*
6564
* domain_state_setup - initialize the cache for a new domain type.
65+
*
66+
* Note: we can't re-use the same cache struct for a new domain type,
67+
* since there's no provision for releasing the DomainConstraintRef.
68+
* If a call site needs to deal with a new domain type, we just leak
69+
* the old struct for the duration of the query.
6670
*/
67-
static void
68-
domain_state_setup(DomainIOData *my_extra, Oid domainType, bool binary,
69-
MemoryContext mcxt)
71+
static DomainIOData *
72+
domain_state_setup(Oid domainType, bool binary, MemoryContext mcxt)
7073
{
74+
DomainIOData *my_extra;
7175
Oid baseType;
72-
MemoryContext oldcontext;
7376

74-
/* Mark cache invalid */
75-
my_extra->domain_type = InvalidOid;
77+
my_extra = (DomainIOData *) MemoryContextAlloc(mcxt, sizeof(DomainIOData));
7678

7779
/* Find out the base type */
7880
my_extra->typtypmod = -1;
@@ -95,16 +97,16 @@ domain_state_setup(DomainIOData *my_extra, Oid domainType, bool binary,
9597
fmgr_info_cxt(my_extra->typiofunc, &my_extra->proc, mcxt);
9698

9799
/* Look up constraints for domain */
98-
oldcontext = MemoryContextSwitchTo(mcxt);
99-
my_extra->constraint_list = GetDomainConstraints(domainType);
100-
MemoryContextSwitchTo(oldcontext);
100+
InitDomainConstraintRef(domainType, &my_extra->constraint_ref, mcxt);
101101

102102
/* We don't make an ExprContext until needed */
103103
my_extra->econtext = NULL;
104104
my_extra->mcxt = mcxt;
105105

106106
/* Mark cache valid */
107107
my_extra->domain_type = domainType;
108+
109+
return my_extra;
108110
}
109111

110112
/*
@@ -118,7 +120,10 @@ domain_check_input(Datum value, bool isnull, DomainIOData *my_extra)
118120
ExprContext *econtext = my_extra->econtext;
119121
ListCell *l;
120122

121-
foreach(l, my_extra->constraint_list)
123+
/* Make sure we have up-to-date constraints */
124+
UpdateDomainConstraintRef(&my_extra->constraint_ref);
125+
126+
foreach(l, my_extra->constraint_ref.constraints)
122127
{
123128
DomainConstraintState *con = (DomainConstraintState *) lfirst(l);
124129

@@ -215,20 +220,16 @@ domain_in(PG_FUNCTION_ARGS)
215220

216221
/*
217222
* We arrange to look up the needed info just once per series of calls,
218-
* assuming the domain type doesn't change underneath us.
223+
* assuming the domain type doesn't change underneath us (which really
224+
* shouldn't happen, but cope if it does).
219225
*/
220226
my_extra = (DomainIOData *) fcinfo->flinfo->fn_extra;
221-
if (my_extra == NULL)
227+
if (my_extra == NULL || my_extra->domain_type != domainType)
222228
{
223-
my_extra = (DomainIOData *) MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
224-
sizeof(DomainIOData));
225-
domain_state_setup(my_extra, domainType, false,
226-
fcinfo->flinfo->fn_mcxt);
229+
my_extra = domain_state_setup(domainType, false,
230+
fcinfo->flinfo->fn_mcxt);
227231
fcinfo->flinfo->fn_extra = (void *) my_extra;
228232
}
229-
else if (my_extra->domain_type != domainType)
230-
domain_state_setup(my_extra, domainType, false,
231-
fcinfo->flinfo->fn_mcxt);
232233

233234
/*
234235
* Invoke the base type's typinput procedure to convert the data.
@@ -275,20 +276,16 @@ domain_recv(PG_FUNCTION_ARGS)
275276

276277
/*
277278
* We arrange to look up the needed info just once per series of calls,
278-
* assuming the domain type doesn't change underneath us.
279+
* assuming the domain type doesn't change underneath us (which really
280+
* shouldn't happen, but cope if it does).
279281
*/
280282
my_extra = (DomainIOData *) fcinfo->flinfo->fn_extra;
281-
if (my_extra == NULL)
283+
if (my_extra == NULL || my_extra->domain_type != domainType)
282284
{
283-
my_extra = (DomainIOData *) MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
284-
sizeof(DomainIOData));
285-
domain_state_setup(my_extra, domainType, true,
286-
fcinfo->flinfo->fn_mcxt);
285+
my_extra = domain_state_setup(domainType, true,
286+
fcinfo->flinfo->fn_mcxt);
287287
fcinfo->flinfo->fn_extra = (void *) my_extra;
288288
}
289-
else if (my_extra->domain_type != domainType)
290-
domain_state_setup(my_extra, domainType, true,
291-
fcinfo->flinfo->fn_mcxt);
292289

293290
/*
294291
* Invoke the base type's typreceive procedure to convert the data.
@@ -326,20 +323,17 @@ domain_check(Datum value, bool isnull, Oid domainType,
326323

327324
/*
328325
* We arrange to look up the needed info just once per series of calls,
329-
* assuming the domain type doesn't change underneath us.
326+
* assuming the domain type doesn't change underneath us (which really
327+
* shouldn't happen, but cope if it does).
330328
*/
331329
if (extra)
332330
my_extra = (DomainIOData *) *extra;
333-
if (my_extra == NULL)
331+
if (my_extra == NULL || my_extra->domain_type != domainType)
334332
{
335-
my_extra = (DomainIOData *) MemoryContextAlloc(mcxt,
336-
sizeof(DomainIOData));
337-
domain_state_setup(my_extra, domainType, true, mcxt);
333+
my_extra = domain_state_setup(domainType, true, mcxt);
338334
if (extra)
339335
*extra = (void *) my_extra;
340336
}
341-
else if (my_extra->domain_type != domainType)
342-
domain_state_setup(my_extra, domainType, true, mcxt);
343337

344338
/*
345339
* Do the necessary checks to ensure it's a valid domain value.

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