From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>,
        Andres Freund <andres@anarazel.de>,
        "Tsunakawa,
    Takayuki" <tsunakawa.takay@jp.fujitsu.com>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        Tomas Vondra <tomas.vondra@2ndquadrant.com>,
        Bruce Momjian <bruce@momjian.us>,
        "Ideriha,
    Takeshi" <ideriha.takeshi@jp.fujitsu.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
        Michael Paquier <michael.paquier@gmail.com>,
        David Steele <david@pgmasters.net>,
        Craig Ringer <craig@2ndquadrant.com>
Subject: Re: Protect syscache from bloating with negative cache entries
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Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Wed, 06 Mar 2019 13:09:15 -0500"
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Date: Wed, 06 Mar 2019 15:17:11 -0500
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Robert Haas <robertmhaas@gmail.com> writes:
> OK, so this is getting simpler, but I'm wondering why we need
> dlist_move_tail() at all.  It is a well-known fact that maintaining
> LRU ordering is expensive and it seems to be unnecessary for our
> purposes here.

Yeah ... LRU maintenance was another thing that used to be in the
catcache logic and was thrown out as far too expensive.  Your idea
of just using a clock sweep instead seems plausible.

			regards, tom lane