Re: CASE WHEN idiomatic for functions with side-effect?

Many thanks Tom and David for clarifying the semantics. /Joel

Re: CASE WHEN idiomatic for functions with side-effect?

"Joel Jacobson" writes: > Is it idiomatic and safe to use > SELECT > CASE boolean_expression WHEN TRUE THEN function_with_side_effects() END > in a query to ensure the function_with_side_effects() is only > execute if boolean_expression is true? As long as function_with_side_effects() is

Re: CASE WHEN idiomatic for functions with side-effect?

On Tue, Jan 12, 2021 at 1:14 AM Joel Jacobson wrote: > Is it idiomatic and safe to use > > SELECT > CASE boolean_expression WHEN TRUE THEN function_with_side_effects() END > As long as function_with_side_effects() is defined volatile it is forced to be executed at runtime, once per row. That

CASE WHEN idiomatic for functions with side-effect?

Is it idiomatic and safe to use SELECT CASE boolean_expression WHEN TRUE THEN function_with_side_effects() END ... in a query to ensure the function_with_side_effects() is only execute if boolean_expression is true? function_with_side_effects() is known to be a normal function, and not an

Re: functions with side effect

On Thu, Jul 19, 2018 at 8:10 PM Tom Lane wrote: > =?UTF-8?Q?Torsten_F=C3=B6rtsch?= writes: > > I know that. My question was about the execution order of f1 and f2 in > > "SELECT f1(), f2()". In theory they can be executed in any order. But > since > > the side effect in nextval determines the

Re: functions with side effect

=?UTF-8?Q?Torsten_F=C3=B6rtsch?= writes: > I know that. My question was about the execution order of f1 and f2 in > "SELECT f1(), f2()". In theory they can be executed in any order. But since > the side effect in nextval determines the result of currval, I am asking if > that order is

Re: functions with side effect

On 07/19/2018 09:43 AM, Torsten Förtsch wrote: On Thu, Jul 19, 2018 at 6:35 PM Adrian Klaver > wrote: On 07/19/2018 07:15 AM, Torsten Förtsch wrote: > Hi, > > assuming > > SELECT nextval('s'), currval('s'); > > or >

Re: functions with side effect

Very interesting question. postgres=# create sequence s; CREATE SEQUENCE postgres=# select currval('s'), nextval('s'); ERROR:  currval of sequence "s" is not yet defined in this session postgres=# select nextval('s'), currval('s');  nextval | currval -+-    1 |   1 We

Re: functions with side effect

On 07/19/2018 09:43 AM, Torsten Förtsch wrote: On Thu, Jul 19, 2018 at 6:35 PM Adrian Klaver > wrote: On 07/19/2018 07:15 AM, Torsten Förtsch wrote: > Hi, > > assuming > > SELECT nextval('s'), currval('s'); > > or >

Re: functions with side effect

On Thu, Jul 19, 2018 at 6:35 PM Adrian Klaver wrote: > On 07/19/2018 07:15 AM, Torsten Förtsch wrote: > > Hi, > > > > assuming > > > > SELECT nextval('s'), currval('s'); > > > > or > > > > SELECT * FROM (VALUES (nextval('s'), currval('s'))) t; > > > > is there any guarantee that the 2 output

Re: functions with side effect

On 07/19/2018 07:15 AM, Torsten Förtsch wrote: Hi, assuming SELECT nextval('s'), currval('s'); or SELECT * FROM (VALUES (nextval('s'), currval('s'))) t; is there any guarantee that the 2 output values are the same? Assuming you are only working in single session:

Re: functions with side effect

Torsten Förtsch wrote: > assuming > > SELECT nextval('s'), currval('s'); > > or > > SELECT * FROM (VALUES (nextval('s'), currval('s'))) t; > > is there any guarantee that the 2 output values are the same? You can use at EXPLAIN (VERBOSE) output to see if it will work in this special case,

functions with side effect

Hi, assuming SELECT nextval('s'), currval('s'); or SELECT * FROM (VALUES (nextval('s'), currval('s'))) t; is there any guarantee that the 2 output values are the same? Thanks, Torsten