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Documentation of the system catalogs, directed toward PostgreSQL developers

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<entry>any OID column</entry>

<entry>

OID of the object within its system catalog, or NULL if the

object is not a general database object

object is not a general database object.

For advisory locks it is used to distinguish the two key

spaces (<literal>1</> for an int8 key, <literal>2</> for two

int4 keys).

</entry>

</row>

<row>

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<chapter id="functions">

<title>Functions and Operators</title>

<para>

<function>pg_advisory_lock</> locks an application-defined resource,

which can be identified either by a single 64-bit key value or two

32-bit key values (note that these two key spaces do not overlap). If

32-bit key values (note that these two key spaces do not overlap).

The key type is specified in <literal>pg_locks.objid</>. If

another session already holds a lock on the same resource, the

function will wait until the resource becomes available. The lock

is exclusive. Multiple lock requests stack, so that if the same resource