Hi
2014-08-22 9:05 GMT+02:00 David G Johnston <david.g.johns...@gmail.com>: > Piotr Gasidło wrote > > Hello, > > > > I found strange PostgreSQL 9.3 behavior: > > > >> select now()::timestamp, 'now()'::timestamp; > > now | timestamp > > ----------------------------+---------------------------- > > 2014-08-22 08:34:00.883268 | 2014-08-22 08:34:00.883268 > > > > Second column is now() in single apostrophes. > > > > Now, I tried similar function, clock_timestamp() and get: > > > >> select clock_timestamp()::timestamp, 'clock_timestamp()'::timestamp; > > ERROR: invalid input syntax for type timestamp: "clock_timestamp()" > > LINE 1: select clock_timestamp()::timestamp, 'clock_timestamp()'::ti... > > ^ > > > > Why is NOW() so special? Where is it documented? And why not working with > > other timestamp returning internal functions? > > > >> select version(); > > version > > > > > -------------------------------------------------------------------------------------------------------------------------------------- > > PostgreSQL 9.3.4 on amd64-portbld-freebsd10.0, compiled by FreeBSD clang > > version 3.3 (tags/RELEASE_33/final 183502) 20130610, 64-bit > > (1 wiersz) > > > > > > -- > > Piotr Gasidło > > SELECT ' now** '::timestamp --works > > Pretty much any symbol before or after the word now is allowed and you > still > get a valid result. Putting a letter or number anywhere in the string > causes an input syntax error. > > Tested on 9.0 > > As for documentation: > > http://www.postgresql.org/docs/9.2/interactive/datetime-input-rules.html > > 2.b > > 'now' is a "special string" as referenced in this rule > > The tokenizer must be constructed to throw away whitespace and any symbols > except those used in normal timestamps (~ [:/-]) > > <tests 'now-'> > > Yep, ^ gives me an error. > > That appendix section is missing considerable detail that I've inferred > from > the observed behavior - though some of the gaps are filled in once you've > read the following: > > http://www.postgresql.org/docs/9.2/interactive/datatype-datetime.html > > The above also explains that the special SQL keywords cannot be used as > string literals though as is often the case it omits any discussion as to > why. The fact that they are functions obviously does not preclude them > from > also being keywords... > > Most likely its this way for SQL standards compatibility reasons. > > Do you have a use-case you'd like to share or is this curiosity after > accidentally finding out that 'now'::timestamp actually works? > > David J. > > > there are more than "now" postgres=# select 'now'::timestamp; timestamp ---------------------------- 2014-08-22 09:08:26.956702 (1 row) postgres=# select 'tomorrow'::timestamp; timestamp --------------------- 2014-08-23 00:00:00 (1 row) postgres=# select 'today'::timestamp; timestamp --------------------- 2014-08-22 00:00:00 (1 row) postgres=# select 'yesterday'::timestamp; timestamp --------------------- 2014-08-21 00:00:00 (1 row) Regards Pavel > > > > > > -- > View this message in context: > http://postgresql.1045698.n5.nabble.com/SELECT-NOW-OK-SELECT-CLOCK-TIMESTAMP-ERROR-tp5815823p5815826.html > Sent from the PostgreSQL - general mailing list archive at Nabble.com. > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
