fix string outputs from UDF (#250)

* fix string outputs from UDF

* use first() instead of only()

Author: aplavin

src/api.jl

@@ -274,7 +274,7 @@ end
 function sqlite3_result_text(context::Ptr{Cvoid}, value::AbstractString)
     return ccall( (:sqlite3_result_text, libsqlite),
         Cvoid, (Ptr{Cvoid}, Ptr{UInt8}, Cint, Ptr{Cvoid}),
-        context, value, sizeof(value)+1, SQLITE_TRANSIENT)
+        context, value, sizeof(value), SQLITE_TRANSIENT)
 end
 # SQLITE_API void sqlite3_result_text16(sqlite3_context*, const void*, int, void(*)(void*));
 # SQLITE_API void sqlite3_result_blob(sqlite3_context*, const void*, int n, void(*)(void*));

test/runtests.jl

@@ -181,6 +181,11 @@ SQLite.register(db, SQLite.regexp, nargs=2, name="regexp")
 r = DBInterface.execute(db, SQLite.@sr_str("SELECT LastName FROM Employee WHERE BirthDate REGEXP '^\\d{4}-08'")) |> columntable
 @test r[1][1] == "Peacock"
 
+SQLite.register(db, identity, nargs=1, name="identity")
+r = DBInterface.execute(db, """SELECT identity("abc") as x, "abc" == identity("abc") as cmp""") |> columntable
+@test first(r.x) == "abc"
+@test first(r.cmp) == 1
+
 @test_throws AssertionError SQLite.register(db, triple, nargs=186)
 SQLite.register(db, triple, nargs=1)
 r = DBInterface.execute(db, "SELECT triple(Total) FROM Invoice ORDER BY InvoiceId LIMIT 5") |> columntable