>> On Aug 23, 2025, at 03:11, Tom Lane <t...@sss.pgh.pa.us> wrote:
>>
>>
>> v2-0001 takes care of that, and also adopts your suggestion in [1]
>> about not using two calls of pushJsonbValueScalar where one would do.
>> I also did a bit more micro-optimization in appendKey, appendValue,
>> appendElement to avoid redundant copying, because perf testing showed
>> that appendElement is still a hot-spot for jsonb_agg. Patches 0002
>> and 0003 are unchanged.
>>
>
>
A few more suggestions for pushJsonValue():
+ /* If an object or array is pushed, recursively push its contents */
+ if (jbval->type == jbvObject)
{
pushJsonbValue(pstate, WJB_BEGIN_OBJECT, NULL);
for (i = 0; i < jbval->val.object.nPairs; i++)
@@ -581,32 +607,29 @@ pushJsonbValue(JsonbParseState **pstate,
JsonbIteratorToken seq,
pushJsonbValue(pstate, WJB_KEY,
&jbval->val.object.pairs[i].key);
pushJsonbValue(pstate, WJB_VALUE,
&jbval->val.object.pairs[i].value);
}
-
- return pushJsonbValue(pstate, WJB_END_OBJECT, NULL);
+ pushJsonbValue(pstate, WJB_END_OBJECT, NULL);
+ return;
}
To push WJB_BEGIN_OBJECT and WJB_END_OBJECT, we can directly call
pushJsonValueScalar(), because once entering pushJsonbValue, they will meet the
check of (seq != WJB_ELEM && seq != WJB_VALUE). Directly calling
pushJsonValueScalar() will saves one level of recursion.
- if (jbval && (seq == WJB_ELEM || seq == WJB_VALUE) && jbval->type ==
jbvArray)
+ if (jbval->type == jbvArray)
{
pushJsonbValue(pstate, WJB_BEGIN_ARRAY, NULL);
for (i = 0; i < jbval->val.array.nElems; i++)
{
pushJsonbValue(pstate, WJB_ELEM,
&jbval->val.array.elems[i]);
}
-
- return pushJsonbValue(pstate, WJB_END_ARRAY, NULL);
+ pushJsonbValue(pstate, WJB_END_ARRAY, NULL);
+ return;
}
Same thing for pushing WJB_BEGIN_ARRAY and WJB_END_ARRAY.
And for pushJsonbValueScalar():
- (*pstate)->size = 4;
+ ppstate->size = 4; /* initial guess at
array size */
Can we do lazy allocation? Initially assume size = 0, only allocate memory when
pushing the first element? This way, we won’t allocate memory for empty objects
and arrays.
Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/
