PostgreSQL V9.6 LWLock实现分析(三)

表X-XX

Wait Event Type

Wait Event Name

Description

Lock[1]

relation

Waiting to acquire a lock on a relation.

extend

Waiting to extend a relation.

page

Waiting to acquire a lock on page of a relation.

tuple

Waiting to acquire a lock on a tuple.

transactionid

Waiting for a transaction to finish.

virtualxid

Waiting to acquire a virtual xid lock.

speculative token

Waiting to acquire a speculative insertion lock.

object

Waiting to acquire a lock on a non-relation database object.

userlock

Waiting to acquire a userlock.

advisory

Waiting to acquire an advisory user lock.

BufferPin[2]

BufferPin

Waiting to acquire a pin on a buffer.

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[1] The backend is waiting for a heavyweightlock. Heavyweight locks, also known as lock manager locks or simply locks,primarily protect SQL-visible objects such as tables. However, they are alsoused to ensure mutual exclusion for certain internal operations such asrelation extension. wait_event will identify the type of lock awaited.

[2] The server process is waiting to access to adata buffer during a period when no other process can be examining that buffer.Buffer pin waits can be protracted if another process holds an open cursorwhich last read data from the buffer in question