How do I replace a comma separated list of strings with the first occurrence?

Question

WHERE MATCH (COALESCE(f1, f2, f3)) AGAINST (?) > 0
WHERE MATCH (COALESCE(f1)) AGAINST (?) > 0

Wanted:

WHERE MATCH (f1) AGAINST (?) > 0
WHERE MATCH (f1) AGAINST (?) > 0

Need to substritute COALESCE(f1, f2, f2, ...) with just f1 , that is the first string if multiple string are present (separated by , ) or just the string itself.

I'm working on this :

#\s*match\s*\((\s*coalesce\s*\((.+)\s*\))\s*\)\s+against#/i

And i'm capturing both what's inside MATCH (1, what's need to be replaced) and what's inside COALESCE (2, the replacement).

How do I substituite 1 with the first value inside 2?

Answer 1

Replace should start at COALESCE but the previous part must match. Use \\K for resetting after (where replacing should start). So the first part could look like MATCH\\s*\\(\\K here starts replacing and pattern continues: \\s*COALESCE\\s*\\(\\s*([^,)]+) ... capturing in first capture group.

And the optional part (?:,[^)]*)? to meet a closing bracket. For the AGAINST part a lookahead can be used: (?=\\)\\s*AGAINST) . So the whole pattern could be:

/MATCH\s*\(\K\s*COALESCE\s*\(\s*([^,)]+)(?:,[^)]*)?\)(?=\)\s*AGAINST)/i

And replace with captured $1 . Test at regex101.com

Answer 2

You can just use the following to match:

(MATCH\s*\()COALESCE\(([^,)\s]+)(?:\s*,[^)]+)?\)

And replace with $1$2

See DEMO