Horton

Re: reducing the footprint of ScanKeyword (was Re: Large writable variables)

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, Andrew Gierth <andrew@tao11.riddles.org.uk>, John Naylor <jcnaylor@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2018-12-26T19:03:57Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> My bet is, and has been for quite a while, that we'll have to go for a
> hand-written recursive descent type parser.

I will state right up front that that will happen over my dead body.

It's impossible to write correct RD parsers by hand for any but the most
trivial, conflict-free languages, and what we have got to deal with
is certainly neither of those; moreover, it's a constantly moving target.
We'd be buying into an endless landscape of parser bugs if we go that way.
It's *not* worth it.

			regards, tom lane

Commits

  1. Use perfect hashing, instead of binary search, for keyword lookup.

  2. Reduce the size of the fmgr_builtin_oid_index[] array.

  3. Replace the data structure used for keyword lookup.