In general, this lock mode will be acquired by any command that modifies data in a table. The commands UPDATE, DELETE, and INSERT acquire this lock mode on the target table (in addition to ACCESS SHARE locks on any other referenced tables). ROW EXCLUSIVEĬonflicts with the SHARE, SHARE ROW EXCLUSIVE, EXCLUSIVE, and ACCESS EXCLUSIVE lock modes.
#Native access no compatible update found update#
The SELECT FOR UPDATE and SELECT FOR SHARE commands acquire a lock of this mode on the target table(s) (in addition to ACCESS SHARE locks on any other tables that are referenced but not selected FOR UPDATE/FOR SHARE).
ROW SHAREĬonflicts with the EXCLUSIVE and ACCESS EXCLUSIVE lock modes. In general, any query that only reads a table and does not modify it will acquire this lock mode. The SELECT command acquires a lock of this mode on referenced tables. Notice in particular that some lock modes are self-conflicting (for example, an ACCESS EXCLUSIVE lock cannot be held by more than one transaction at a time) while others are not self-conflicting (for example, an ACCESS SHARE lock can be held by multiple transactions).Ĭonflicts with the ACCESS EXCLUSIVE lock mode only. For example, it might acquire ACCESS EXCLUSIVE lock and later acquire ACCESS SHARE lock on the same table.) Non-conflicting lock modes can be held concurrently by many transactions. (However, a transaction never conflicts with itself. Two transactions cannot hold locks of conflicting modes on the same table at the same time. The only real difference between one lock mode and another is the set of lock modes with which each conflicts (see Table 13-2). To some extent the names reflect the typical usage of each lock mode - but the semantics are all the same. Remember that all of these lock modes are table-level locks, even if the name contains the word "row" the names of the lock modes are historical. You can also acquire any of these locks explicitly with the command LOCK. The list below shows the available lock modes and the contexts in which they are used automatically by PostgreSQL.
0 kommentar(er)
