Horton

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

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

View thread View on postgr.es
From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Steele <david@pgmasters.net>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Pavel Stehule <pavel.stehule@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Petr Fedorov <petr.fedorov@phystech.edu>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-03-15T17:35:12Z
Lists: pgsql-bugs, pgsql-hackers 
David Steele <david@pgmasters.net> writes:
> On 12/15/20 9:03 AM, Peter Eisentraut wrote:
>> Here is a new patch for this.  This now follows the implementation that 
>> Tom has suggested:  Leave date_part() alone, add a new set of extract() 
>> functions, and map the SQL EXTRACT construct to those.  I have basically 
>> just copied over the implementations from my previous patch and placed 
>> them next to the existing date_part() implementations.  So all the 
>> behavior is still the same as in the previous patches.
>> 
>> One thing I still need to look into is how to not lose all the test 
>> coverage for date_part().  But that should be fairly mechanical, so I'm 
>> leaving it off in this version.

> Tom, what do you think of the updated patch?

Oh, I didn't think I was on the hook to review this ;-)

Anyway, taking a quick look at the v4 patch, the only complaint
I have is that it seems a bit bulky and brute-force to duplicate
so much code.  Is it feasible to share most of the implementation
between old and new functions, returning (say) an int64 that can
then be converted to either numeric or float8 by a wrapper?  That
would also reduce the pressure to duplicate all the test cases.

(I don't intend this complaint as a deal-breaker; Peter may well
have considered this alternative already and rejected it for good
reasons.)

			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.