Noah Misch wrote: > On Sun, Apr 17, 2011 at 04:55:51PM +0100, Jack Douglas wrote: > > I discovered the 'fields' option of 'interval', but i can't figure out > > from the docs how it is supposed to work. Are "hour to minute" and "day > > to minute" really the same thing? And if not, in what circumstances are > > they treated differently? > > As of version 8.4, they behave identically. The code has this comment, some > form of which probably belongs in the documentation: > > /* > * Our interpretation of intervals with a limited set of fields is > * that fields to the right of the last one specified are zeroed out, > * but those to the left of it remain valid. Thus for example there > * is no operational difference between INTERVAL YEAR TO MONTH and > * INTERVAL MONTH. In some cases we could meaningfully enforce that > * higher-order fields are zero; for example INTERVAL DAY could reject > * nonzero "month" field. However that seems a bit pointless when we > * can't do it consistently. (We cannot enforce a range limit on the > * highest expected field, since we do not have any equivalent of > * SQL's <interval leading field precision>.) > * > * Note: before PG 8.4 we interpreted a limited set of fields as > * actually causing a "modulo" operation on a given value, potentially > * losing high-order as well as low-order information. But there is > * no support for such behavior in the standard, and it seems fairly > * undesirable on data consistency grounds anyway. Now we only > * perform truncation or rounding of low-order fields. > */ I am lost on how we could mention that in the docs. -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
