锁的类型
/* NoLock is not a lock mode, but a flag value meaning "don't get a lock" */
#define NoLock 0
#define AccessShareLock 1 /* SELECT */
#define RowShareLock 2 /* SELECT FOR UPDATE/FOR SHARE */
#define RowExclusiveLock 3 /* INSERT, UPDATE, DELETE */
#define ShareUpdateExclusiveLock 4 /* VACUUM (non-FULL),ANALYZE, CREATE
* INDEX CONCURRENTLY */
#define ShareLock 5 /* CREATE INDEX (WITHOUT CONCURRENTLY) */
#define ShareRowExclusiveLock 6 /* like EXCLUSIVE MODE, but allows ROW
* SHARE */
#define ExclusiveLock 7 /* blocks ROW SHARE/SELECT...FOR
* UPDATE */
#define AccessExclusiveLock 8 /* ALTER TABLE, DROP TABLE, VACUUM
* FULL, and unqualified LOCK TABLE */可以加锁的对象
LOCKTAG_RELATION, /* whole relation */
/* ID info for a relation is DB OID + REL OID; DB OID = 0 if shared */
LOCKTAG_RELATION_EXTEND, /* the right to extend a relation */
/* same ID info as RELATION */
LOCKTAG_PAGE, /* one page of a relation */
/* ID info for a page is RELATION info + BlockNumber */
LOCKTAG_TUPLE, /* one physical tuple */
/* ID info for a tuple is PAGE info + OffsetNumber */
LOCKTAG_TRANSACTION, /* transaction (for waiting for xact done) */
/* ID info for a transaction is its TransactionId */
LOCKTAG_VIRTUALTRANSACTION, /* virtual transaction (ditto) */
/* ID info for a virtual transaction is its VirtualTransactionId */
LOCKTAG_SPECULATIVE_TOKEN, /* speculative insertion Xid and token */
/* ID info for a transaction is its TransactionId */
LOCKTAG_OBJECT, /* non-relation database object */
/* ID info for an object is DB OID + CLASS OID + OBJECT OID + SUBID */
/*
* Note: object ID has same representation as in pg_depend and
* pg_description, but notice that we are constraining SUBID to 16 bits.
* Also, we use DB OID = 0 for shared objects such as tablespaces.
*/
LOCKTAG_USERLOCK, /* reserved for old contrib/userlock code */
LOCKTAG_ADVISORY /* advisory user locks */查询锁以及进程的相关视图
/*锁信息*/
select * from pg_locks;
/*记录表和类似于表这种具有列的结构*/
select * from pg_class;
/* 查询进程信息*/
select * from pg_stat_activity
/*查询锁的相关信息*/
select t.locktype,
t2.datname,
t1.relname,
mode,
t3.usename,
application_name,
client_addr,
query
from pg_locks t, pg_class t1, pg_database t2, pg_stat_activity t3
where t.DATABASE = t2.oid
and t.relation = t1.oid
and t.pid = t3.pid参考 pg中关于AccessShareLock和ExclusiveLock的问题中德哥的回答
