Convert non-binary columns to String type (#153)

* Convert non-binary columns to String type

Fixes #150.

The issue here is that the C API, by default, says that TEXT columns are
of type MYSQL_TYPE_BLOB, from what I gathered because C doesn't really
have a true "string" type, so it doesn't really matter if it's blob or
string anyway. But, upon further investigation, I found in the
MYSQL_FIELD flags field documentation a bit switch to tell whether a
column is in fact binary or not. Using this, we can now detect
accurately whether a column can be treated as a string or should be
returned as a byte vector. The tests added test the return value of
columns defined as TEXT and BLOB and that they are accurately
distinguished on the Julia side.

* fix failing test

Author: quinnj

src/MySQL.jl

@@ -260,10 +260,11 @@ end
 Base.close(conn::Connection) = DBInterface.close!(conn)
 Base.isopen(conn::Connection) = API.isopen(conn.mysql)
 
-function juliatype(field_type, notnullable, isunsigned)
+function juliatype(field_type, notnullable, isunsigned, isbinary)
     T = API.juliatype(field_type)
     T2 = isunsigned ? unsigned(T) : T
-    return notnullable ? T2 : Union{Missing, T2}
+    T3 = !isbinary && T2 == Vector{UInt8} ? String : T2
+    return notnullable ? T3 : Union{Missing, T3}
 end
 
 include("execute.jl")

src/api/apitypes.jl

@@ -90,6 +90,7 @@ struct MYSQL_FIELD
 end
 notnullable(field) = (field.flags & NOT_NULL_FLAG) > 0
 isunsigned(field) = (field.flags & UNSIGNED_FLAG) > 0
+isbinary(field) = (field.flags & BINARY_FLAG) > 0
 
 const MYSQL_FIELD_OFFSET = Cuint
 const MYSQL_ROW = Ptr{Ptr{UInt8}}

src/api/consts.jl

@@ -205,6 +205,7 @@ const MYSQL_TIMESTAMP_TIME     = 2
 
 const NOT_NULL_FLAG = UInt32(1)
 const UNSIGNED_FLAG = UInt32(32)
+const BINARY_FLAG = UInt32(128)
 const MYSQL_NO_DATA = 100
 
 const MYSQL_DEFAULT_PORT = 3306

src/execute.jl

@@ -152,7 +152,7 @@ function DBInterface.execute(conn::Connection, sql::AbstractString, params=(); m
         nfields = API.numfields(result)
         fields = API.fetchfields(result, nfields)
         names = [ccall(:jl_symbol_n, Ref{Symbol}, (Ptr{UInt8}, Csize_t), x.name, x.name_length) for x in fields]
-        types = [juliatype(x.field_type, API.notnullable(x), API.isunsigned(x)) for x in fields]
+        types = [juliatype(x.field_type, API.notnullable(x), API.isunsigned(x), API.isbinary(x)) for x in fields]
     elseif API.fieldcount(conn.mysql) == 0
         rows_affected = API.affectedrows(conn.mysql)
         names = Symbol[]

src/prepare.jl

@@ -51,7 +51,7 @@ function DBInterface.prepare(conn::Connection, sql::AbstractString)
     if result.ptr != C_NULL
         fields = API.fetchfields(result, nfields)
         names = [ccall(:jl_symbol_n, Ref{Symbol}, (Ptr{UInt8}, Csize_t), x.name, x.name_length) for x in fields]
-        types = [juliatype(x.field_type, API.notnullable(x), API.isunsigned(x)) for x in fields]
+        types = [juliatype(x.field_type, API.notnullable(x), API.isunsigned(x), API.isbinary(x)) for x in fields]
         valuehelpers = [API.BindHelper() for i = 1:nfields]
         values = [API.MYSQL_BIND(valuehelpers[i].length, valuehelpers[i].is_null) for i = 1:nfields]
         foreach(1:nfields) do i

test/runtests.jl

@@ -203,3 +203,21 @@ DBInterface.execute(stmt, -1)
 res = DBInterface.execute(conn, "select id from negative_int") |> columntable
 @test length(res) == 1
 @test res[1][1] === Int32(-1)
+
+
+DBInterface.execute(conn, "DROP TABLE if exists text_field")
+DBInterface.execute(conn, "CREATE TABLE text_field (id int(11), t text)")
+stmt = DBInterface.prepare(conn, "INSERT INTO text_field (id, t) VALUES (?, ?);")
+DBInterface.execute(stmt, [-1, "hey there sailor"])
+res = DBInterface.execute(conn, "select id, t from text_field") |> columntable
+@test length(res) == 2
+@test res[2][1] === "hey there sailor"
+
+
+DBInterface.execute(conn, "DROP TABLE if exists blob_field")
+DBInterface.execute(conn, "CREATE TABLE blob_field (id int(11), t blob)")
+stmt = DBInterface.prepare(conn, "INSERT INTO blob_field (id, t) VALUES (?, ?);")
+DBInterface.execute(stmt, [-1, "hey there sailor"])
+res = DBInterface.execute(conn, "select id, t from blob_field") |> columntable
+@test length(res) == 2
+@test res[2][1] == [0x68, 0x65, 0x79, 0x20, 0x74, 0x68, 0x65, 0x72, 0x65, 0x20, 0x73, 0x61, 0x69, 0x6c, 0x6f, 0x72]