Hello,
my scenario is this: I have a *SEGMENT* table with two text fields, *source*
and *target*. From the user, I get the following input:
/source pattern/
/target pattern/
Where both patterns are regexes and moreover the target pattern contains
references to the source in the following way:
Supposing *source* matches the /source pattern/, the $/n/ expressions inside
the /target pattern/ correspond to the captured groups inside *source*.
Example:
Source: 123 source text
Target: 123 target text
Source pattern: ([0-9]+) source text
Target pattern: $1 target text
This yields a successful match since $1 in the /target pattern/ is replaced
by "123" from the first captured group in *source* and the resulting string,
"123 target text", matches the /target pattern/.
I would like to execute a query which for a given /source pattern/ and
/target pattern/ returns all rows from the *SEGMENT* table where *source*
matches the /source pattern/ and *target* matches the /target pattern/ after
it has its references replaced with the actual captured groups.
I believe this is not possible since *regexp_replace* expects a string as
its /replacement/ argument which is not enough in this case. This kind of
stuff is easy in e.g. C# where for regex replace you can provide a function
which receives the (in this case) reference index as its argument and you
can build the replacement string using external knowledge.
However, as I am no pro in Postgres, I may be missing something and
therefore I ask: is it possible to somehow mimic the behavior of
hypothetical *regexp_replace* which would accept a function of the
to-be-replaced value and would return the replacement string based on that.
And as I am thinking about it, even that would not suffice since that
function would need to access not only the to-be-replaced value but also the
corresponding source pattern match.
Still, isn't there some super clever way to do that?
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