Re: Making jsonb_agg() faster

> On Nov 3, 2025, at 04:56, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> PFA v3, rebased over 8a27d418f, no substantive changes whatever.
>
> regards, tom lane
>

I am on vacation this week, I only find a hour in the evening and did an eyeball review without actually tracing and testing this patch set. Overall, the changes are solid and look good to me. Only a few small comments on 0001:

1 - jsonpath_exec.c
```
@@ -2874,8 +2874,7 @@ executeKeyValueMethod(JsonPathExecContext *cxt, JsonPathItem *jsp,
{
JsonBaseObjectInfo baseObject;
JsonbValue obj;
- JsonbParseState *ps;
- JsonbValue *keyval;
+ JsonbInState ps;
Jsonb *jsonb;

if (tok != WJB_KEY)
@@ -2889,7 +2888,8 @@ executeKeyValueMethod(JsonPathExecContext *cxt, JsonPathItem *jsp,
tok = JsonbIteratorNext(&it, &val, true);
Assert(tok == WJB_VALUE);

- ps = NULL;
+ memset(&ps, 0, sizeof(ps));
+
```

In elsewhere of the patch, you all use “JsonbInState ps = {0}” to do the initialization, only this place uses memset(). Can we keep consistent and use {0} here also. I see there is a “continue” and a “break” before the memset(), maybe you want to avoid unnecessary initialization. I guess that is a tiny saving, but if you think that saving is worthwhile, I’m fine with keeping the current code.

2 - jsonb_util.c
```
+ case TIMETZOID:
+ /* pass-by-reference */
+ oldcontext = MemoryContextSwitchTo(outcontext);
+ v->val.datetime.value = datumCopy(v->val.datetime.value,
+ false, 12);
```

Instead of hard-coding 12, can we use "sizeof(TimeTzADT)” for better readability?

3 - jsonb_plperl.c
```
+ {
+ /* XXX Ugly hack */
+ jsonb_state->result = palloc(sizeof(JsonbValue));
+ memcpy(jsonb_state->result, &out, sizeof(JsonbValue));
+ }
```
And
```
+ else
+ {
+ /* XXX Ugly hack */
+ jsonb_state->result = out;
+ }
```

You left two “ugly hack” comments. Maybe add a short description for why they are hack and what can be improved in the future.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/