We'll respond shortly.
One of our tables was using an hstore to collect data (a really big json object). We discovered that the primary database on staging was using PG 9.1.3 while our acceptance & production apps were using 9.1.4. Pushing this very large (58K) object into the hstore caused a Postgres failure:
ActiveRecord::StatementInvalid: PGError: ERROR: cannot execute INSERT in a read-only transaction : INSERT INTO “xxxx” (”created_at”, “data”, “updated_at”, “user_id”) VALUES ($1, $2, $3, $4) RETURNING “id”
while saving the same data into our acceptance app did not cause the error.
We suspect that there is a bug in PG 9.1.3 when inserting “big” strings into an hstore that is fixed in 9.1.4.
We promoted a new 9.1.4 db on our staging app. This cleared our problem.
We were able to stream the contents of a table to the user without loading the whole dataset into memory.
It’s in Denver this year.