*
* element_type is the array element type (must be a valid array element type)
* rcontext is where to keep working state
+ * subcontext is a flag determining whether to use a separate memory context
*
* Note: there are two common schemes for using accumArrayResult().
* In the older scheme, you start with a NULL ArrayBuildState pointer, and
* once per element. In this scheme you always end with a non-NULL pointer
* that you can pass to makeArrayResult; you get an empty array if there
* were no elements. This is preferred if an empty array is what you want.
+ *
+ * It's possible to choose whether to create a separate memory context for the
+ * array build state, or whether to allocate it directly within rcontext.
+ *
+ * When there are many concurrent small states (e.g. array_agg() using hash
+ * aggregation of many small groups), using a separate memory context for each
+ * one may result in severe memory bloat. In such cases, use the same memory
+ * context to initialize all such array build states, and pass
+ * subcontext=false.
+ *
+ * In cases when the array build states have different lifetimes, using a
+ * single memory context is impractical. Instead, pass subcontext=true so that
+ * the array build states can be freed individually.
*/
ArrayBuildState *
-initArrayResult(Oid element_type, MemoryContext rcontext)
+initArrayResult(Oid element_type, MemoryContext rcontext, bool subcontext)
{
ArrayBuildState *astate;
- MemoryContext arr_context;
+ MemoryContext arr_context = rcontext;
/* Make a temporary context to hold all the junk */
- arr_context = AllocSetContextCreate(rcontext,
- "accumArrayResult",
- ALLOCSET_DEFAULT_MINSIZE,
- ALLOCSET_DEFAULT_INITSIZE,
- ALLOCSET_DEFAULT_MAXSIZE);
+ if (subcontext)
+ arr_context = AllocSetContextCreate(rcontext,
+ "accumArrayResult",
+ ALLOCSET_DEFAULT_MINSIZE,
+ ALLOCSET_DEFAULT_INITSIZE,
+ ALLOCSET_DEFAULT_MAXSIZE);
astate = (ArrayBuildState *)
MemoryContextAlloc(arr_context, sizeof(ArrayBuildState));
astate->mcontext = arr_context;
- astate->alen = 64; /* arbitrary starting array size */
+ astate->private_cxt = subcontext;
+ astate->alen = (subcontext ? 64 : 8); /* arbitrary starting array size */
astate->dvalues = (Datum *)
MemoryContextAlloc(arr_context, astate->alen * sizeof(Datum));
astate->dnulls = (bool *)
if (astate == NULL)
{
/* First time through --- initialize */
- astate = initArrayResult(element_type, rcontext);
+ astate = initArrayResult(element_type, rcontext, true);
}
else
{
/*
* makeArrayResult - produce 1-D final result of accumArrayResult
*
+ * Note: only releases astate if it was initialized within a separate memory
+ * context (i.e. using subcontext=true when calling initArrayResult).
+ *
* astate is working state (must not be NULL)
* rcontext is where to construct result
*/
dims[0] = astate->nelems;
lbs[0] = 1;
- return makeMdArrayResult(astate, ndims, dims, lbs, rcontext, true);
+ return makeMdArrayResult(astate, ndims, dims, lbs, rcontext,
+ astate->private_cxt);
}
/*
* beware: no check that specified dimensions match the number of values
* accumulated.
*
+ * Note: if the astate was not initialized within a separate memory context
+ * (that is, initArrayResult was called with subcontext=false), then using
+ * release=true is illegal. Instead, release astate along with the rest of its
+ * context when appropriate.
+ *
* astate is working state (must not be NULL)
* rcontext is where to construct result
* release is true if okay to release working state
/* Clean up all the junk */
if (release)
+ {
+ Assert(astate->private_cxt);
MemoryContextDelete(astate->mcontext);
+ }
return PointerGetDatum(result);
}
* initArrayResultArr - initialize an empty ArrayBuildStateArr
*
* array_type is the array type (must be a valid varlena array type)
- * element_type is the type of the array's elements
+ * element_type is the type of the array's elements (lookup if InvalidOid)
* rcontext is where to keep working state
+ * subcontext is a flag determining whether to use a separate memory context
*/
ArrayBuildStateArr *
-initArrayResultArr(Oid array_type, Oid element_type, MemoryContext rcontext)
+initArrayResultArr(Oid array_type, Oid element_type, MemoryContext rcontext,
+ bool subcontext)
{
ArrayBuildStateArr *astate;
- MemoryContext arr_context;
+ MemoryContext arr_context = rcontext; /* by default use the parent ctx */
+
+ /* Lookup element type, unless element_type already provided */
+ if (! OidIsValid(element_type))
+ {
+ element_type = get_element_type(array_type);
+
+ if (!OidIsValid(element_type))
+ ereport(ERROR,
+ (errcode(ERRCODE_DATATYPE_MISMATCH),
+ errmsg("data type %s is not an array type",
+ format_type_be(array_type))));
+ }
/* Make a temporary context to hold all the junk */
- arr_context = AllocSetContextCreate(rcontext,
- "accumArrayResultArr",
- ALLOCSET_DEFAULT_MINSIZE,
- ALLOCSET_DEFAULT_INITSIZE,
- ALLOCSET_DEFAULT_MAXSIZE);
+ if (subcontext)
+ arr_context = AllocSetContextCreate(rcontext,
+ "accumArrayResultArr",
+ ALLOCSET_DEFAULT_MINSIZE,
+ ALLOCSET_DEFAULT_INITSIZE,
+ ALLOCSET_DEFAULT_MAXSIZE);
/* Note we initialize all fields to zero */
astate = (ArrayBuildStateArr *)
MemoryContextAllocZero(arr_context, sizeof(ArrayBuildStateArr));
astate->mcontext = arr_context;
+ astate->private_cxt = subcontext;
/* Save relevant datatype information */
astate->array_type = array_type;
arg = DatumGetArrayTypeP(dvalue);
if (astate == NULL)
- {
- /* First time through --- initialize */
- Oid element_type = get_element_type(array_type);
-
- if (!OidIsValid(element_type))
- ereport(ERROR,
- (errcode(ERRCODE_DATATYPE_MISMATCH),
- errmsg("data type %s is not an array type",
- format_type_be(array_type))));
- astate = initArrayResultArr(array_type, element_type, rcontext);
- }
+ astate = initArrayResultArr(array_type, InvalidOid, rcontext, true);
else
- {
Assert(astate->array_type == array_type);
- }
oldcontext = MemoryContextSwitchTo(astate->mcontext);
/* Clean up all the junk */
if (release)
+ {
+ Assert(astate->private_cxt);
MemoryContextDelete(astate->mcontext);
+ }
return PointerGetDatum(result);
}
*
* input_type is the input datatype (either element or array type)
* rcontext is where to keep working state
+ * subcontext is a flag determining whether to use a separate memory context
*/
ArrayBuildStateAny *
-initArrayResultAny(Oid input_type, MemoryContext rcontext)
+initArrayResultAny(Oid input_type, MemoryContext rcontext, bool subcontext)
{
ArrayBuildStateAny *astate;
Oid element_type = get_element_type(input_type);
/* Array case */
ArrayBuildStateArr *arraystate;
- arraystate = initArrayResultArr(input_type, element_type, rcontext);
+ arraystate = initArrayResultArr(input_type, InvalidOid, rcontext, subcontext);
astate = (ArrayBuildStateAny *)
MemoryContextAlloc(arraystate->mcontext,
sizeof(ArrayBuildStateAny));
/* Let's just check that we have a type that can be put into arrays */
Assert(OidIsValid(get_array_type(input_type)));
- scalarstate = initArrayResult(input_type, rcontext);
+ scalarstate = initArrayResult(input_type, rcontext, subcontext);
astate = (ArrayBuildStateAny *)
MemoryContextAlloc(scalarstate->mcontext,
sizeof(ArrayBuildStateAny));
MemoryContext rcontext)
{
if (astate == NULL)
- astate = initArrayResultAny(input_type, rcontext);
+ astate = initArrayResultAny(input_type, rcontext, true);
if (astate->scalarstate)
(void) accumArrayResult(astate->scalarstate,
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