hmysql

A (low level) MySQL driver in pure Haskell, supports handling large resultset in streaming mode.

Currently, it is just a very basic and naive implementation.

Build & Play

cabal sandbox init && cabal install --only-dependencies && cabal build (Windows not supported, yet)

For demonstration, a very simple MySQL client repl is provided.

./dist/build/repl/repl -u$username --pass$password -d$database

or ./dist/build/repl/repl -s/var/run/mysqld/mysqld.sock

or ./dist/build/repl/repl -? for more argvs.

then, feed it with some sqls,

Flags {host = "localhost", port = "3306", user = "root", pass = "", db = ""}
Greeting
  { protocol = 10
  , version = "5.5.35-0ubuntu0.13.10.2"
  , tid = 57
  , salt1 = "yi$s8]MI"
  , caps = 63487
  , lang = 8
  , status = 2
  , salt2 = "eBZ{!-[ekiO-"
  }
hmysql> select 1
[ Packed
    { header = PacketHeader { hLen = 2 , hSeq = 4 }
    , payload = RowData [ LCS "1" ]
    }
]

for verbose output, just prefix ':' to the sql,

hmysql> :select 1
RSRes
  ResultSetPackets
    { rColCount =
        Packed
          { header = PacketHeader { hLen = 1 , hSeq = 1 }
          , payload = ColCount 1
          }
    , rColDefs =
        [ Packed
            { header = PacketHeader { hLen = 23 , hSeq = 2 }
            , payload =
                ColDef
                  { fdb = LCS ""
                  , ftbl = LCS ""
                  , forgTbl = LCS ""
                  , fName = LCS "1"
                  , forgName = LCS ""
                  , fcharset = 63
                  , flen = 1
                  , ftype = 8
                  , flags = 129
                  , fdecimals = 0
                  }
            }
        ]
    , rEOF1 =
        Packed
          { header = PacketHeader { hLen = 5 , hSeq = 3 }
          , payload = EOF { warningCount = 0 , statusFlags = 2 }
          }
    , rRows =
        [ Packed
            { header = PacketHeader { hLen = 2 , hSeq = 4 }
            , payload = RowData [ LCS "1" ]
            }
        ]
    , rEOF2 =
        Packed
          { header = PacketHeader { hLen = 5 , hSeq = 5 }
          , payload = EOF { warningCount = 0 , statusFlags = 2 }
          }
    }

for streaming mode, prefix "!" to the sql

hmysql> use somedb
OKRes
  Packed
    { header = PacketHeader { hLen = 7 , hSeq = 1 } , payload = OK }
hmysql> select count(*) from a_large_table
[ Packed
    { header = PacketHeader { hLen = 7 , hSeq = 4 }
    , payload = RowData [ LCS "214573185" ]
    }
]
hmysql> !select * from a_large_table --warning: lots of outputs! but can be processed in constant space.
[ Packed
    { header = PacketHeader { hLen = 250 , hSeq = 25 }
    , payload =
        RowData
          [ LCS "084"
          , LCS "2013-08-08 16:09:23"
          , LCS "2"
          ...
          , Null
          , Null
          ]
    }
]

...

Bugs & Known Issues

• Does not support MySQL packet larger than 16Mbytes.
• Does not support multi-resultset yet.
• Lack of MySQL packet validations, such as sequence num, integrity of packets, etc.
• Stream resultset accessing API is ... awkward
• ...