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babelfish_extensions
Babelfish for PostgreSQL provides the capability for PostgreSQL to work with applications written for Microsoft SQL Server. Babelfish understands the SQL Server wire-protocol and T-SQL, the Microsoft SQL Server query and procedural language, so you don’t have to switch database drivers or rewrite all of your application queries.
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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
Was just about to write that AWS does that, but no, it's only for MS SQL Server: https://babelfishpg.org/, https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide....
NOTE:
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Hence, a higher number means a more popular project.