Thread: checking if jsonb was detoasted and releasing memory

Igor Stassiy <istassiy@gmail.com> writes:
> Let us say that the datum of type Datum contains a Jsonb* type.
> Then after the call

> Jsonb *jb = DatumGetJsonb(datum);

> the jb might point to a palloc'ed structure, in case detoasting took place.
> So the question is if this is the right way to free up the memory after
> checking that the jb was detoasted?

> if ((void *)jb != DatumGetPointer(datum))
> pfree(jb); // free if detoasted

For the most part the answer is "don't bother".  Except in very narrow
cases, it's not worth it to clean up such values retail as opposed to
letting the next evaluation context reset get rid of them in bulk.

The code you proposed will work, but it's ugly and usually a net waste
of cycles.  It also embeds assumptions we might want to change someday.

            regards, tom lane