Обсуждение: Unnecessary use of .* in examples
The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/13/functions-matching.html Description: In the table for the ~ (and friends) operator, every example has a pointless set of '.*' surrounding the text to be matched. These unnecessary operators add visual clutter making the examples both harder to read and understand, and since they're official examples, they teach bad habits. That is to say, 'thomas' ~ 'thom' is the exact same regex as 'thomas' ~ '.*thom.*' but the first is shorter, easier to read and easier to understand, and, presumably, faster as well. Operator Description Example(s) text ~ text → boolean String matches regular expression, case sensitively 'thomas' ~ '.*thom.*' → t text ~* text → boolean String matches regular expression, case insensitively 'thomas' ~* '.*Thom.*' → t text !~ text → boolean String does not match regular expression, case sensitively 'thomas' !~ '.*thomas.*' → f text !~* text → boolean String does not match regular expression, case insensitively 'thomas' !~* '.*vadim.*' → t
On Mon, 2021-02-01 at 05:46 +0000, PG Doc comments form wrote: > Page: https://www.postgresql.org/docs/13/functions-matching.html > Description: > > In the table for the ~ (and friends) operator, every example has a pointless > set of '.*' surrounding the text to be matched. These unnecessary operators > add visual clutter making the examples both harder to read and understand, > and since they're official examples, they teach bad habits. > > That is to say, 'thomas' ~ 'thom' is the exact same regex as 'thomas' ~ > '.*thom.*' but the first is shorter, easier to read and easier to > understand, and, presumably, faster as well. > > Operator > > Description > > Example(s) > > text ~ text → boolean > > String matches regular expression, case sensitively > > 'thomas' ~ '.*thom.*' → t > > text ~* text → boolean > > String matches regular expression, case insensitively > > 'thomas' ~* '.*Thom.*' → t > > text !~ text → boolean > > String does not match regular expression, case sensitively > > 'thomas' !~ '.*thomas.*' → f > > text !~* text → boolean > > String does not match regular expression, case insensitively > > 'thomas' !~* '.*vadim.*' → t I agree that that is comewhat confusing for people who understand regular expressions. On the other hand, the example should show some special characters, so that people who don't know regular expressions understand that this is more than substring matching. Perhaps 'thomas' ~ '^thom' and so on? Yours, Laurenz Albe
Laurenz Albe <laurenz.albe@cybertec.at> writes:
> On Mon, 2021-02-01 at 05:46 +0000, PG Doc comments form wrote:
>> In the table for the ~ (and friends) operator, every example has a pointless
>> set of '.*' surrounding the text to be matched. These unnecessary operators
>> add visual clutter making the examples both harder to read and understand,
>> and since they're official examples, they teach bad habits.
> I agree that that is comewhat confusing for people who understand
> regular expressions. On the other hand, the example should show some
> special characters, so that people who don't know regular expressions
> understand that this is more than substring matching.
> Perhaps 'thomas' ~ '^thom' and so on?
There are examples just a bit further down that include special
characters. I agree with the OP that the useless ".*"s add nothing
except confusion as to the semantics; but I don't think we need these
very first examples to use a lot of bells and whistles.
Maybe what would be better is to have an example with embedded .*
such as 'thomas' ~ 't.*m'.
regards, tom lane
On Mon, 2021-02-01 at 10:08 -0500, Tom Lane wrote: > > On Mon, 2021-02-01 at 05:46 +0000, PG Doc comments form wrote: > > > In the table for the ~ (and friends) operator, every example has a pointless > > > set of '.*' surrounding the text to be matched. These unnecessary operators > > > add visual clutter making the examples both harder to read and understand, > > > and since they're official examples, they teach bad habits. > > > I agree that that is comewhat confusing for people who understand > > regular expressions. On the other hand, the example should show some > > special characters, so that people who don't know regular expressions > > understand that this is more than substring matching. > > > Perhaps 'thomas' ~ '^thom' and so on? > > There are examples just a bit further down that include special > characters. I agree with the OP that the useless ".*"s add nothing > except confusion as to the semantics; but I don't think we need these > very first examples to use a lot of bells and whistles. > > Maybe what would be better is to have an example with embedded .* > such as 'thomas' ~ 't.*m'. I agree, and thanks for improving it in https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=9522085ac917af66dba29939af328ae67300f10a Yours, Laurenz Albe