pgsql: Use psprintf to simplify gtsvectorout()

Use psprintf to simplify gtsvectorout()

The buffer allocation was correct, but looked archaic and scary:

- It was weird to calculate the buffer size before determining which
format string was used. With the same effort, we could've used the
right-sized buffer for each branch.

- Commit aa0d3504560 added one more possible return string ("all true
bits"), but didn't adjust the code at the top of the function to
calculate the returned string's max size. It was not a live bug,
because the new string was smaller than the existing ones, but
seemed wrong in principle.

- Use of sprintf() is generally eyebrow-raising these days

Switch to psprintf(). psprintf() allocates a larger buffer than what
was allocated before, 128 bytes vs 80 bytes, which is acceptable as
this code is not performance or space critical.

Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/54c29fb0-edf2-48ea-9814-44e918bbd6e8@iki.fi

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3ab2668d48476e31d8809fbb36c9ee739cc444e1

Modified Files
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src/backend/utils/adt/tsgistidx.c | 17 ++++-------------
1 file changed, 4 insertions(+), 13 deletions(-)