Horton

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

Vik Fearing <vik@postgresfriends.org>

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From: Vik Fearing <vik@postgresfriends.org>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, 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: 2020-05-25T16:01:07Z
Lists: pgsql-bugs, pgsql-hackers 
On 5/25/20 3:28 PM, Peter Eisentraut wrote:
> 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).

I think what would be better is to have a specific date_part function
for each part and have extract translate to the appropriate one.  This
is particularly interesting for epoch but it would also allow us to
return the correct type mandated by the spec.

(I would also accept a specific date_part per return type instead of per
part, that would probably even be better.)
-- 
Vik Fearing

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.