Transaction isolation and UNION queries - Mailing list pgsql-admin

From Bob Smith
Subject Transaction isolation and UNION queries
Date
Msg-id 0A27C204-4AC6-11D7-978F-0003933DD370@h-e.com
Whole thread Raw
Responses Re: Transaction isolation and UNION queries  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-admin
I have a question about transaction isolation that I can't find an
answer to in the docs.  I'm working with a database that has some data
split over two tables.  One table is the ultimate destination for all
the data, the other is a "pending" table which holds rows during data
entry.  Rows from the pending table are moved to the permanent table
once data entry is complete.  For some purposes I want to see rows from
both tables, so I do a UNION.  My question is, with only read committed
isolation, could a commit by another transaction make changes appear
between the separate parts of the UNION query?  In other words, could a
row appear to be missing or duplicated because a transaction that was
moving the row from pending to permanent committed while the UNION was
running?

Thanks!

Bob Smith
Hammett & Edison, Inc.
bsmith@h-e.com


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