"T.J.Farrell" <T.J.Farrell@wanadoo.fr> writes:
> I was wondering about the performance incidence of :
> SELECT * FROM table1 WHERE UPPER(field1) LIKE
> UPPER('%thomas%');
> versus:
> SELECT * FROM table1 WHERE field1 ~~ '%thomas%'
Of course "~~" is just an alternate spelling of LIKE, and is
case-sensitive, so the above two queries are not equivalent.
Perhaps you meant to refer to "~*" which is a case-insensitive
regex match ... but then you'd need a different pattern.
Anyway, if you keep an index on upper(field1) then the first form
is the way to go, since the system can use a left-anchored pattern
as an index range restriction.
regards, tom lane