Re: Maximum number of columns in a table
От | Gerry Scales |
---|---|
Тема | Re: Maximum number of columns in a table |
Дата | |
Msg-id | FEAB96F4E8574EAAA6BA8918D0A2D616@GPS071 обсуждение исходный текст |
Ответ на | Maximum number of columns in a table ("Gerry Scales" <gerry@tbstbs.net>) |
Список | pgsql-general |
Thanks Sam, that's excellent advice. If a developer doesn't jump in with a definitive formula, that is the path I will take. Regards Gerry ----- Original Message ----- From: "Sam Mason" <sam@samason.me.uk> To: <pgsql-general@postgresql.org> Sent: Sunday, April 12, 2009 7:23 AM Subject: Re: [GENERAL] Maximum number of columns in a table > On Sun, Apr 12, 2009 at 05:33:35AM +1000, Gerry Scales wrote: >> The FAQs state "Maximum number of columns in a table? 250-1600 >> depending on column types". >> >> Is there a location which gives instructions for calculating whether a >> number of columns of different types can be accommodated? >> >> I have a situation where I need to load tables from another database >> which may theoretically contain up to 1000 columns per table and this >> information will determine whether I need to rebuild PostgreSQL with >> a larger blocksize. Splitting into multiple tables is not always an >> easy option. > > I think the only definitive advice I can give would be to try it and > see how it works. That said the pg_column_size function may be of > use and I'd have a look at how variable length fields (i.e. CHAR(n), > VARCHAR(n), TEXT, NUMERIC) and TOAST are handled. Fixed size fields, > such as integers are going to be fine for you and you should be able > to fit more than a thousand integers into a row, but text values will > depend on the size of the text you're inserting. I think that either > short strings (i.e. less than 8 characters on average) or large bits of > text, because they're getting TOASTed, should be OK. Also note that > NULL values get compressed into a bitmap at the beginning of the tuple > and so don't take up much space. > > Hope that helps! > > > -- > Sam http://samason.me.uk/ > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general
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