Horton

Re: Since '2001-09-09 01:46:40'::timestamp microseconds are lost when extracting epoch

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, Petr Fedorov <petr.fedorov@phystech.edu>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-05-25T13:43:32Z
Lists: pgsql-bugs, pgsql-hackers 
Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> One problem (other than perhaps performance, tbd.) is that this would no 
> longer allow processing infinite timestamps, since numeric does not 
> support infinity.  It could be argued that running extract() on infinite 
> timestamps isn't very useful, but it's something to consider explicitly.

I wonder if it's time to fix that, ie introduce +-Infinity into numeric.c.
This isn't the first time we've seen issues with numeric not being a
superset of float, and it won't be the last.

At first glance there's no free bits in the on-disk format for numeric,
but we could do something by defining the low-order bits of the header
word for a NaN to distinguish between real NaN and +/- infinity.
It looks like those bits should reliably be zero right now.

			regards, tom lane

Commits

  1. Fix inconsistent equalfuncs.c behavior for FuncCall.funcformat.

  2. Doc: fix discussion of how to get real Julian Dates.

  3. Doc: document EXTRACT(JULIAN ...), improve Julian Date explanation.

  4. Change return type of EXTRACT to numeric

  5. Improve our ability to regurgitate SQL-syntax function calls.

  6. Add more tests for EXTRACT of date type

  7. Expose internal function for converting int64 to numeric

  8. Change floating-point output format for improved performance.