Hi Olaf, I can't speak for SQL in general, but if you're targeting PostgreSQL note that the hasql library uses a binary wire format. You'll need to use parameterized queries to benefit from this, but it would let you avoid encoding digits to ASCII. Ollie On Tue, 9 Aug 2022, at 8:34 PM, Olaf Klinke wrote:
Dear Café,
I was discussing with a friend the fastest way to shovel data into a SQL database after parsing the raw (textual) data with Haskell. I am concerned about numeric conversion: In my experience parsing the file structure is fast. The majority of the time is spent converting strings of digits to numbers. I hoped that once Haskell has constructed a Double, the backend driver can hand that binary value over to the database engine. But Database.HDBC.Statement has a field
orginalQuery :: String
and HDBC has functions
prepare :: Connection -> String -> IO Statement run :: Connection -> String -> [SqlValue] -> IO Integer
which makes me wonder whether the backend constructs a complete SQL query statement in form of a string (including the SqlValues), and hands that to the database driver to parse. Is that indeed so? If yes, the numbers should never be parsed in the first place: The DB will do that anyways. I might as well construct a new CSV file and let the database do a bulk insert on that. The above is specific to the HDBC backend. If there are other backends/frameworks that do the marshalling more efficiently, please let me know.
Thanks Olaf
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