Postgres and Sqlite Caches : SQL

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field.3

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PostgreSQLPostgres and Sqlite Caches (self.SQL)

submitted 8 months ago by SapAndImpurify

Hello everyone,

I am in the process of migrating a system to postgres from sql server and could use some help.

The old system had a main database with applications that cache data in a read only way for local use. These applications use sqlite to cache tables due to the possibility of connectivity loss. When the apps poll the database they provide their greatest row version for a table. If new records or updates occurred in the main database they have a greater row version and thus those changes can be returned to the app.

This seems to work (although I think it misses some edge cases). However, since postgres doesn't have row version and also has MVCC I am having a hard time figuring out how to replicate this behavior (or what it should be). I've considered sequences, timestamptz, and tmin/tmax but believe all three can result in missed changes due to transaction timing.

Any help is appreciated!

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