The semantics of isc_tpb_autocommit

From Vlad Horsun:

A simplified overview of the autocommit code:

When a transaction, marked as TRA_autocommit performs any of following actions, it is marked also as TRA_perform_autocommit

• insert
• update
• delete
• select with lock
• post event

The TRA_perform_autocommit flag is checked when

• the engine receives input message
• the engine sends an output message
• the engine starts to execute a request
• the engine finishes executing a DDL request

When the TRA_perform_autocommit flag is detected, the engine runs on-commit triggers (not for DDL, that looks like a bug) and performs commit retaining. A new transaction will have TRA_autocommit flag set and TRA_perform_autocommit not set.