Thread: Table vs. row level locks confusion

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

What I wonder is, if I do

BEGIN;
LOCK table1 IN ROW EXCLUSIVE MODE;

what do I lock?  The table?  A row?  Which row?

Clarification appreciated.

-- 
Peter Eisentraut   peter_e@gmx.net   http://funkturm.homeip.net/~peter

Peter Eisentraut <peter_e@gmx.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