Handling transactions in Python DBI module
frank at chagford.com
Thu Feb 11 00:28:47 EST 2016
"Chris Angelico" wrote in message
news:CAPTjJmphJvtCKUB6Qr-vp_1epEWxBgQxmfKEPMOhQp3pAPGG+A at mail.gmail.com...
> When I advise my students on basic databasing concepts, I recommend
> this structure:
> conn = psycopg2.connect(...)
> with conn, conn.cursor() as cur:
Does this automatically issue a 'conn.commit()' on exit?
I have found that this is important, for the following reason.
If you issue a bare SELECT to PostgreSQL, it executes it without creating
any locks. However, if it is inside a transaction, it does create a lock (I
forget exactly which one).
Because psycopg2 silently executes 'BEGIN TRANSACTION', your SELECTs always
happen inside a transaction whether you specify it or not. If you do not
issue a conn.commit(), the locks do not get cleared.
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