`report_journal_ledger` is auto-vacuumed as any transient model, but has some
ondelete="cascade" constraints that auto-remove subtables when a record is removed,
doing this operation very slow when selecting these sub-records.
Letting default ondelete="set null" would result in same performance bottleneck,
as the select on sub-table is performed the same for setting "null" value on them.
As a solution, and for avoiding a costly index operation, we delete by SQL sub-tables
rows in advance.
A bit of extra logic has been added for avoiding to remove that records if it's not
the turn of vacuum the parent table.
When there are a lot of account.move.line (several millions) and print any of
the Qweb reports, that will generate also a lot of transient objects.
As these objects are created with an "insert" query, the cleaning normally
triggered by the count of the records in transient tables is not done, so only
the cleaning based on the age of the records is processed (by default, records
older than 1 hours are deleted), but the cron task is only ran one time per
day. For large setups this can lead to memory errors at that point. This change
prevents the memory error by executing the transient record cleanup for the
report models in this module in SQL.
Pedro M. Baeza
Patrick Tombez
hveficent