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: John Naylor <john.naylor@2ndquadrant.com>
Cc: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, Joerg Sonnenberger <joerg@bec.de>, David Rowley <david.rowley@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2019-01-08T22:53:25Z
Lists: pgsql-hackers

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John Naylor <john.naylor@2ndquadrant.com> writes:
> -As for the graph algorithm, I'd have to play with it to understand
> how it works.

I improved the comment about how come the hash table entry assignment
works.  One thing I'm not clear about myself is

	# A cycle-free graph is either empty or has some vertex of degree 1.

That sounds like a standard graph theory result, but I'm not familiar
with a proof for 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.