I’ve recently made some comparisons between HaskellDB and HDBC. My gut feeling is that I’d like to use HaskellDB due to its type safety and that it allows me to abstract away from SQL—something in me twitches every time I see strings containing SQL mixed in with other code, no matter what language it is. However there are some things that confuse me with HaskellDB. After overcoming the initial puzzlement that I seem to hit whenever I look at a Haskell API I stumbled on the apparent lack of support for primary keys. This surprised me and to check if I overlooked something I wrote the following code:

module Main where
 
import System.Environment
import System.IO
import Database.HaskellDB.HSQL.SQLite3
import Database.HaskellDB.DBSpec
 
testDBOpts = DBOptions { useBString=False }
 
sqliteOptions= SQLiteOptions { filepath="replace me", mode=ReadMode }
 
main :: IO ()
main = do
    dbfn <- fmap (!! 0) getArgs
    let options = sqliteOptions { filepath=dbfn }
    sqliteConnect options (dbToDBSpec False "extracted.db") >>= print

This is the surprising output when I point this to two different databases. The first database has no primary key:

% sqlite3 test1.db .dump
BEGIN TRANSACTION;
CREATE TABLE person (name text  not null,
                     age int);
COMMIT;

and the DBInfo looks the way I expected:

% ./extract test1.db 
DBInfo {dbname = "extracted.db", opts = DBOptions {useBString = False},
tbls = [TInfo {tname = "person", cols = [CInfo {cname = "name",
descr = (StringT,False)},CInfo {cname = "age", descr = (StringT,True)}]}]}

The second database does have a primary key:

% sqlite3 test2.db .dump
BEGIN TRANSACTION;
CREATE TABLE person (name text primary key not null, age int);
COMMIT;

but not only does the DBInfo lack any mention of it, it also contains the table info twice:

% ./extract test2.db 
DBInfo {dbname = "extracted.db", opts = DBOptions {useBString = False},
tbls = [TInfo {tname = "person", cols = [CInfo {cname = "name",
descr = (StringT,False)},CInfo {cname = "age", descr = (StringT,True)}]},
TInfo {tname = "person", cols = [CInfo {cname = "name",
descr = (StringT,False)},CInfo {cname = "age", descr = (StringT,True)}]}]}

Am I doing something fundamentally wrong or does HaskellDB not support the notion of a primary key?

Is it a bug in HaskellDB that the second extracted DBInfo contains two instances of TInfo when the database clearly only has one table?

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