Обсуждение: Document Upper Limit for NAMEDATELEN in pgsql 9.5+

Поиск
Список
Период
Сортировка

Document Upper Limit for NAMEDATELEN in pgsql 9.5+

От
Kevin Day
Дата:
Postgresql 9.5+ may now fail to compile if NAMEDATELEN has been set absurdly large (In my case, 384).

The file src/backend/utils/adt/levenshtein.c does a static assert on "NAMEDATALEN <= MAX_LEVENSHTEIN_STRLEN" with MAX_LEVENSHTEIN_STRLEN currently set to 255.

When using a gcc version that does not support static asserts, the error message looks like:
- "levenshtein.c:104: error: negative width in bit-field 'static_assert_failure'"

It would be great to be mention this new upper limit on NAMEDATALEN in the documentation.

Here are some places I've looked at:
- src/include/pg_config_manual.h
- http://www.postgresql.org/docs/9.5/static/sql-syntax-lexical.html
- http://www.postgresql.org/docs/9.5/static/runtime-config-preset.html
- https://wiki.postgresql.org/wiki/Todo

While on the subject of NAMEDATALEN, there is a second undocumented place where NAMEDATALEN is defined:
- src/interfaces/ecpg/include/sqlda-native.h

--
Kevin Day

Re: Document Upper Limit for NAMEDATELEN in pgsql 9.5+

От
Tom Lane
Дата:
Kevin Day <thekevinday@gmail.com> writes:
> Postgresql 9.5+ may now fail to compile if NAMEDATELEN has been set
> absurdly large (In my case, 384).
> The file src/backend/utils/adt/levenshtein.c does a static assert on
> "NAMEDATALEN <= MAX_LEVENSHTEIN_STRLEN" with MAX_LEVENSHTEIN_STRLEN
> currently set to 255.

Hmm.  I'm not sure whether 384 is "absurdly large", but I do wonder
why the levenshtein code gets to dictate limits on NAMEDATALEN at all.

Or to put it even more bluntly, I'm not sure that there is anything
whatever about MAX_LEVENSHTEIN_STRLEN that is well thought out.  Why not
rip it out and put some CHECK_FOR_INTERRUPTS tests into the loops instead?

            regards, tom lane