Re: Making jsonb_agg() faster

> On Nov 3, 2025, at 04:56, Tom Lane <tgl@sss.pgh.pa.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
testingthis 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().
Canwe keep consistent and use {0} here also. I see there is a “continue” and a “break” before the memset(), maybe you
wantto avoid unnecessary initialization. I guess that is a tiny saving, but if you think that saving is worthwhile, I’m
finewith 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/