Horton

Re: Some regular-expression performance hacking

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: "Joel Jacobson" <joel@compiler.org>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2021-02-13T17:35:45Z
Lists: pgsql-hackers 
"Joel Jacobson" <joel@compiler.org> writes:
> In total, I scraped the first-page of some ~50k websites,
> which produced 45M test rows to import,
> which when GROUP BY pattern and flags was reduced
> down to 235k different regex patterns,
> and 1.5M different text string subjects.

This seems like an incredibly useful test dataset.
I'd definitely like a copy.

> No is_match differences were detected, good!

Cool ...

> However, there were 23 cases where what got captured differed:

I shall take a closer look at that.

Many thanks for doing this work!

			regards, tom lane

Commits

  1. Suppress unnecessary regex subre nodes in a couple more cases.

  2. Improve memory management in regex compiler.

  3. Extend a test case a little

  4. Allow complemented character class escapes within regex brackets.

  5. Suppress compiler warning in new regex match-all detection code.

  6. Avoid generating extra subre tree nodes for capturing parentheses.

  7. Convert regex engine's subre tree from binary to N-ary style.

  8. Fix regex engine to suppress useless concatenation sub-REs.

  9. Recognize "match-all" NFAs within the regex engine.

  10. Invent "rainbow" arcs within the regex engine.

  11. Make some minor improvements in the regex code.

  12. Display the time when the process started waiting for the lock, in pg_locks, take 2

  13. README/C-comment: document GiST's NSN value

  14. doc: Mention NO DEPENDS ON EXTENSION in its supported ALTER commands