I have developed an application using MS SQL. I have used MS Access for
creating forms to enter data into the database. I am thinking of changing over
to postgresql and would also like to use any other available open source tool
for creating forms. Are there any free applications available for c
Summarizing:
* Lock table - High-level: executes fast, but concurrency problems.
Guarentees about future changes.
Select for update - Low-level, concurrent, ensures data validity and
indicates its modified shortly.
Select for share - Low-level, concurrent, ensures data validity.
Hopefully this
It is not necessary that LOCK TABLE will be the first statement.
(assuming serializable isolation level is snapshot isolation in postgres)
For serializable transaction, snapshot should be taken when the 'BEGIN'
statement is executed, and not when LOCK TABLE succeeds.
Hence, uncommitted changes s
OK. In your example lock table command is used to avoid rollbacks due
to concurrent transaction.
So LOCK TABLE is useful in this situation.
I have one last doubt:
why there is difference between behavior of 'select for update' and
'lock table'.
one causes serialization error and other does no
Thanks Laurenz for quick reply.
If this is the expected behavior then isn't 'Lock table' is just extra
performance penalty and achieves nothing under serializable isolation level.
The serializable isolation level in postgres is infact snapshot isolation.
Suppose a transaction T is using 'lock
Hi,
As per postgres docs, 'Select for update' is used to obtain row level
locks where as 'lock table' is used to obtain table level locks.
Under serializable isolation level, select for update gives error if
rows selected have been modified concurrently.
but 'lock table' does not give such er
