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Re: Table vs. row level locks confusion

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Table vs. row level locks confusion
Date: 2001-09-04 15:01:08
Message-ID: 26359.999615668@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> The following section
> http://www.ca.postgresql.org/devel-corner/docs/postgres/locking-tables.html
> titled "Locking and Tables", has two subsections, "Table-level locks" and
> "Row-level locks".  Under table-level locks we find lock names such as
> RowShareLock and RowExclusiveLock -- are those table-level locks?

Yes, despite the names.  (The various lock-type names are pretty
horrible IMHO, but they are claimed to be Oracle-compatible.)
Anything you do with a LOCK command is a table-level lock.

> Under row-level locks we find no specific lock names mentioned.

The only row-level locking mechanism available to users is
to UPDATE, DELETE, or SELECT FOR UPDATE a particular row.
All rows affected by such a command are locked against other
such commands (but not against plain SELECT).

			regards, tom lane

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