Add macros to make AllocSetContextCreate() calls simpler and safer.

I found that half a dozen (nearly 5%) of our AllocSetContextCreate calls
had typos in the context-sizing parameters.  While none of these led to
especially significant problems, they did create minor inefficiencies,
and it's now clear that expecting people to copy-and-paste those calls
accurately is not a great idea.  Let's reduce the risk of future errors
by introducing single macros that encapsulate the common use-cases.
Three such macros are enough to cover all but two special-purpose contexts;
those two calls can be left as-is, I think.

While this patch doesn't in itself improve matters for third-party
extensions, it doesn't break anything for them either, and they can
gradually adopt the simplified notation over time.

In passing, change TopMemoryContext to use the default allocation
parameters.  Formerly it could only be extended 8K at a time.  That was
probably reasonable when this code was written; but nowadays we create
many more contexts than we did then, so that it's not unusual to have a
couple hundred K in TopMemoryContext, even without considering various
dubious code that sticks other things there.  There seems no good reason
not to let it use growing blocks like most other contexts.

Back-patch to 9.6, mostly because that's still close enough to HEAD that
it's easy to do so, and keeping the branches in sync can be expected to
avoid some future back-patching pain.  The bugs fixed by these changes
don't seem to be significant enough to justify fixing them further back.

Discussion: <[email protected]>

7 files changed, 13 insertions, 37 deletions

diff --git a/contrib/bloom/blinsert.c b/contrib/bloom/blinsert.c
index 78eec5c67e0..0946aa29ecc 100644
--- a/contrib/bloom/blinsert.c
+++ b/contrib/bloom/blinsert.c
@@ -130,9 +130,7 @@ blbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	initBloomState(&buildstate.blstate, index);
 	buildstate.tmpCtx = AllocSetContextCreate(CurrentMemoryContext,
 											  "Bloom build temporary context",
-											  ALLOCSET_DEFAULT_MINSIZE,
-											  ALLOCSET_DEFAULT_INITSIZE,
-											  ALLOCSET_DEFAULT_MAXSIZE);
+											  ALLOCSET_DEFAULT_SIZES);
 	initCachedPage(&buildstate);
 
 	/* Do the heap scan */
@@ -204,9 +202,7 @@ blinsert(Relation index, Datum *values, bool *isnull,
 
 	insertCtx = AllocSetContextCreate(CurrentMemoryContext,
 									  "Bloom insert temporary context",
-									  ALLOCSET_DEFAULT_MINSIZE,
-									  ALLOCSET_DEFAULT_INITSIZE,
-									  ALLOCSET_DEFAULT_MAXSIZE);
+									  ALLOCSET_DEFAULT_SIZES);
 
 	oldCtx = MemoryContextSwitchTo(insertCtx);
 
diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 9c8e3083584..d4f9090f062 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -980,9 +980,7 @@ materializeQueryResult(FunctionCallInfo fcinfo,
 		/* Create short-lived memory context for data conversions */
 		sinfo.tmpcontext = AllocSetContextCreate(CurrentMemoryContext,
 												 "dblink temporary context",
-												 ALLOCSET_DEFAULT_MINSIZE,
-												 ALLOCSET_DEFAULT_INITSIZE,
-												 ALLOCSET_DEFAULT_MAXSIZE);
+												 ALLOCSET_DEFAULT_SIZES);
 
 		/* execute query, collecting any tuples into the tuplestore */
 		res = storeQueryResult(&sinfo, conn, sql);
diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index c0491318c0b..b42de873e0f 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1061,9 +1061,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 	 */
 	tupcontext = AllocSetContextCreate(CurrentMemoryContext,
 									   "file_fdw temporary context",
-									   ALLOCSET_DEFAULT_MINSIZE,
-									   ALLOCSET_DEFAULT_INITSIZE,
-									   ALLOCSET_DEFAULT_MAXSIZE);
+									   ALLOCSET_DEFAULT_SIZES);
 
 	/* Prepare for sampling rows */
 	reservoir_init_selection_state(&rstate, targrows);
diff --git a/contrib/pg_trgm/trgm_regexp.c b/contrib/pg_trgm/trgm_regexp.c
index 3f09a9c718d..005701fcd92 100644
--- a/contrib/pg_trgm/trgm_regexp.c
+++ b/contrib/pg_trgm/trgm_regexp.c
@@ -529,9 +529,7 @@ createTrgmNFA(text *text_re, Oid collation,
 	 */
 	tmpcontext = AllocSetContextCreate(CurrentMemoryContext,
 									   "createTrgmNFA temporary context",
-									   ALLOCSET_DEFAULT_MINSIZE,
-									   ALLOCSET_DEFAULT_INITSIZE,
-									   ALLOCSET_DEFAULT_MAXSIZE);
+									   ALLOCSET_DEFAULT_SIZES);
 	oldcontext = MemoryContextSwitchTo(tmpcontext);
 
 	/*
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index b92f29958f3..daf04385321 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -1315,14 +1315,10 @@ postgresBeginForeignScan(ForeignScanState *node, int eflags)
 	/* Create contexts for batches of tuples and per-tuple temp workspace. */
 	fsstate->batch_cxt = AllocSetContextCreate(estate->es_query_cxt,
 											   "postgres_fdw tuple data",
-											   ALLOCSET_DEFAULT_MINSIZE,
-											   ALLOCSET_DEFAULT_INITSIZE,
-											   ALLOCSET_DEFAULT_MAXSIZE);
+											   ALLOCSET_DEFAULT_SIZES);
 	fsstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
 											  "postgres_fdw temporary data",
-											  ALLOCSET_SMALL_MINSIZE,
-											  ALLOCSET_SMALL_INITSIZE,
-											  ALLOCSET_SMALL_MAXSIZE);
+											  ALLOCSET_SMALL_SIZES);
 
 	/*
 	 * Get info we'll need for converting data fetched from the foreign server
@@ -1695,9 +1691,7 @@ postgresBeginForeignModify(ModifyTableState *mtstate,
 	/* Create context for per-tuple temp workspace. */
 	fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
 											  "postgres_fdw temporary data",
-											  ALLOCSET_SMALL_MINSIZE,
-											  ALLOCSET_SMALL_INITSIZE,
-											  ALLOCSET_SMALL_MAXSIZE);
+											  ALLOCSET_SMALL_SIZES);
 
 	/* Prepare for input conversion of RETURNING results. */
 	if (fmstate->has_returning)
@@ -2294,9 +2288,7 @@ postgresBeginDirectModify(ForeignScanState *node, int eflags)
 	/* Create context for per-tuple temp workspace. */
 	dmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
 											  "postgres_fdw temporary data",
-											  ALLOCSET_SMALL_MINSIZE,
-											  ALLOCSET_SMALL_INITSIZE,
-											  ALLOCSET_SMALL_MAXSIZE);
+											  ALLOCSET_SMALL_SIZES);
 
 	/* Prepare for input conversion of RETURNING results. */
 	if (dmstate->has_returning)
@@ -3481,9 +3473,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.anl_cxt = CurrentMemoryContext;
 	astate.temp_cxt = AllocSetContextCreate(CurrentMemoryContext,
 											"postgres_fdw temporary data",
-											ALLOCSET_SMALL_MINSIZE,
-											ALLOCSET_SMALL_INITSIZE,
-											ALLOCSET_SMALL_MAXSIZE);
+											ALLOCSET_SMALL_SIZES);
 
 	/*
 	 * Get the connection to use.  We do the remote access as the table's
diff --git a/contrib/sepgsql/uavc.c b/contrib/sepgsql/uavc.c
index 10fa9a0b0bc..6e358dbef7c 100644
--- a/contrib/sepgsql/uavc.c
+++ b/contrib/sepgsql/uavc.c
@@ -498,13 +498,11 @@ sepgsql_avc_init(void)
 	int			rc;
 
 	/*
-	 * All the avc stuff shall be allocated on avc_mem_cxt
+	 * All the avc stuff shall be allocated in avc_mem_cxt
 	 */
 	avc_mem_cxt = AllocSetContextCreate(TopMemoryContext,
 										"userspace access vector cache",
-										ALLOCSET_DEFAULT_MINSIZE,
-										ALLOCSET_DEFAULT_INITSIZE,
-										ALLOCSET_DEFAULT_MAXSIZE);
+										ALLOCSET_DEFAULT_SIZES);
 	memset(avc_slots, 0, sizeof(avc_slots));
 	avc_num_caches = 0;
 	avc_lru_hint = 0;
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index c3508f0e13d..949e9a78d92 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -102,9 +102,7 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	data = palloc0(sizeof(TestDecodingData));
 	data->context = AllocSetContextCreate(ctx->context,
 										  "text conversion context",
-										  ALLOCSET_DEFAULT_MINSIZE,
-										  ALLOCSET_DEFAULT_INITSIZE,
-										  ALLOCSET_DEFAULT_MAXSIZE);
+										  ALLOCSET_DEFAULT_SIZES);
 	data->include_xids = true;
 	data->include_timestamp = false;
 	data->skip_empty_xacts = false;