The decoded borsh payload, exactly as stored. Shape varies by name.
Position within the transaction's parsed_events array (0-based).
Part of the row's identity: (signature, eventIndex) is unique, while
signature alone is not for the handful of two-event transactions.
Event struct name — "MintEvent", "TransferEvent", …
Transaction signature — the explorer link and the natural reference.
One decoded mintfx event, addressed by the transaction that emitted it.
The grain is the event, not the transaction and not the
solana_account_transactionrow. A transaction carrying two events is two rows here; on prod that is 8 transactions out of 80,976, so the fan-out is real but negligible — and it is the grain an operator reading "what did the program do" actually wants.