Horton

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

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Thomas Munro <thomas.munro@gmail.com>, Petr Fedorov <petr.fedorov@phystech.edu>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-05-25T13:28:54Z
Lists: pgsql-bugs, pgsql-hackers 
On 2019-12-02 23:52, Thomas Munro wrote:
>> I'm not an expert in floating point math but hopefully it means that no
>> type change is required - double precision can handle it.
> Me neither, but the SQL standard requires us to use an exact numeric
> type, so it's wrong on that level by definition.

I looked into this (changing the return types of date_part()/extract() 
from float8 to numeric).

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.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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.