Em 24/10/2023 13:27, Carlos Alves escreveu: > Hi! > > I need some help to understand why a transaction wiht a row delete aquire a > AccessExclusiveLock and a row update a ExclusiveLock. > > To ilustrate, a made this scenario: > > create table tblock > > ( > > id int primary key, > > value text > > ); > > insert into tblock values (1, 'somevalue'); > > First start Transaction 1: > > begin; > > update tblock set value = 'othervalue' where id = 1; > > -- keep this transaction opened > > After, start Transaction 2: > > begin; > > update tblock set value = 'onemorevalue' where id = 1; > > -- at this point, this transaction assumes a ExclusiveLock in the tuple; > > -- keep this transaction opend > > Then, start Transaction 3: > > begin; > > update tblock set value = 'lastofthevalues' where id = 1; > > -- here i can see this transaction trying to aquire a AccessExclusiveLock in > this tuple > > So, my question is: why a delete row requires a AccessExclusiveLock in the > tuple insteead of ExclusiveLock? > > Bellow, a image of a query over pg_locks: > > PostgreSQL version: 13 > > OS: Centos 7 > > Thanks in advance.
I typed the last command wrong. Should be: Transaction 3: begin; delete from tblock where id = 1; Sorry!
