Horton

RE: [Patch] Optimize dropping of relation buffers using dlist

tsunakawa.takay@fujitsu.com <tsunakawa.takay@fujitsu.com>

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From: "tsunakawa.takay@fujitsu.com" <tsunakawa.takay@fujitsu.com>
To: "k.jamison@fujitsu.com" <k.jamison@fujitsu.com>
Cc: 'Amit Kapila' <amit.kapila16@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, Thomas Munro <thomas.munro@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-12-10T08:28:56Z
Lists: pgsql-hackers 
From: Jamison, Kirk/ジャミソン カーク <k.jamison@fujitsu.com>
> I added comment in 0004 the limitation of optimization when there are TOAST
> relations that use NON-PLAIN strategy. i.e. The optimization works if the data
> types used are integers, OID, bytea, etc. But for TOAST-able data types like text,
> the optimization will be skipped and force a full scan during recovery.

bytea is a TOAST-able type.


+	/*
+	 * Enter the optimization if the total number of blocks to be
+	 * invalidated for all relations is below the full scan threshold.
+	 */
+	if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)

Checking cached here doesn't seem to be necessary, because if cached is false, the control goes to the full scan path as below:

+			if (!cached)
+				goto buffer_full_scan;
+


Regards
Takayuki Tsunakawa

Commits

  1. Fix size overflow in calculation introduced by commits d6ad34f3 and bea449c6.

  2. Optimize DropRelFileNodesAllBuffers() for recovery.

  3. Optimize DropRelFileNodeBuffers() for recovery.

  4. Cache smgrnblocks() results in recovery.

  5. Add a check to prevent overwriting valid data if smgrnblocks() gives a