Post PC era databases twinned with microservices log events rather than transactions. In certain business use cases, such as KYC, account balances require aggregates for totalization. SalesForce (Force.com) uses reverse Lucene queries, CQRS event systems use analytics to totalize, another way is insert projection events into a SQL database. Vent uses projections.
A projection is the name given to the configuration files that Vent uses to interpret EVM events as updates or deletion from SQL tables. They provide an object relational mapping between Solidity events and SQL tables.
> Vent reads specification files called 'projections', parses their contents, and maps EVM LOG event fields to corresponding SQL columns to create or alter database structures. It listens for a stream of block events from Burrow's GRPC service then parses, unpacks, decodes event data, and builds rows to be upserted in matching event tables, rows are upserted atomically in a single database transaction per block.
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