Обсуждение: proposal: prefix function
Hi
can we implement prefix function for fast test if substr is prefix of some string?
create or replace function prefix(str text, substr text)
returns boolean as $$
select substr(str, 1, length(substr)) = substr
$$ language sql;
select substr(str, 1, length(substr)) = substr
$$ language sql;
This function can be very effective in C language. Now it should be implemented with like or regexp, what is significantly more expensive.
Regards
Pavel
On Fri, Sep 21, 2018 at 10:09 AM Pavel Stehule <pavel.stehule@gmail.com> wrote:
Hican we implement prefix function for fast test if substr is prefix of some string?create or replace function prefix(str text, substr text)returns boolean as $$
select substr(str, 1, length(substr)) = substr
$$ language sql;This function can be very effective in C language. Now it should be implemented with like or regexp, what is significantly more expensive.
These would just be wrappers around already existing internal functions, right?
RegardsPavel
Best Regards,
Chris Travers
Head of Database
Saarbrücker Straße 37a, 10405 Berlin
pá 21. 9. 2018 v 12:37 odesílatel Chris Travers <chris.travers@adjust.com> napsal:
On Fri, Sep 21, 2018 at 10:09 AM Pavel Stehule <pavel.stehule@gmail.com> wrote:Hican we implement prefix function for fast test if substr is prefix of some string?create or replace function prefix(str text, substr text)returns boolean as $$
select substr(str, 1, length(substr)) = substr
$$ language sql;This function can be very effective in C language. Now it should be implemented with like or regexp, what is significantly more expensive.These would just be wrappers around already existing internal functions, right?
maybe, I didn't do any research. If not, the implementation is on few lines.
Regards
Pavel
RegardsPavel--Best Regards,Chris TraversHead of DatabaseSaarbrücker Straße 37a, 10405 Berlin
Hi
pá 21. 9. 2018 v 12:37 odesílatel Chris Travers <chris.travers@adjust.com> napsal:
On Fri, Sep 21, 2018 at 10:09 AM Pavel Stehule <pavel.stehule@gmail.com> wrote:Hican we implement prefix function for fast test if substr is prefix of some string?create or replace function prefix(str text, substr text)returns boolean as $$
select substr(str, 1, length(substr)) = substr
$$ language sql;This function can be very effective in C language. Now it should be implemented with like or regexp, what is significantly more expensive.These would just be wrappers around already existing internal functions, right?
It is already - I forgot
starts_with
It is PostgreSQL 11 feature 710d90da1fd8c1d028215ecaf7402062079e99e9
I like when I can do nothing :)
Pavel
RegardsPavel--Best Regards,Chris TraversHead of DatabaseSaarbrücker Straße 37a, 10405 Berlin