SQLite locks up

[uint]

I'm trying to use SQLite with the Using session example. Since at first I was getting a "table does not exist" error, I created a sessions table on my own:

CL-USER> (datafly.db:connect-toplevel :sqlite3 :database-name #P"test.db")
#<DBD.SQLITE3:<DBD-SQLITE3-CONNECTION> {10051B2653}>
CL-USER> (datafly.db:execute (sxql:create-table :sessions ((id :type '(:int 20) :primary-key t :unique t) (session_data :type '(:varchar 2048) :not-null nil :default nil))))
; No value
CL-USER> (datafly.db:disconnect-toplevel)
NIL

It does look like some session data gets stored as I open served pages in my browser, but then when I open a page that actually tries to store some session data (the counter thing from the example), I get:

DB Error: database is locked (Code: BUSY)
   [Condition of type DBI.ERROR:<DBI-DATABASE-ERROR>]

Restarts:
 0: [ABORT] abort thread (#<THREAD "hunchentoot-worker-127.0.0.1:51360" RUNNING {1001DE5113}>)

Backtrace:
  0: ((:METHOD DBI.DRIVER:PREPARE (DBD.SQLITE3:<DBD-SQLITE3-CONNECTION> STRING)) #<DBD.SQLITE3:<DBD-SQLITE3-CONNECTION> {1003595743}> "SELECT session_data FROM sessions WHERE id = ?") [fast-method]
  1: ((:METHOD LACK.MIDDLEWARE.SESSION.STORE:FETCH-SESSION (LACK.MIDDLEWARE.SESSION.STORE.DBI:DBI-STORE T)) #S(LACK.MIDDLEWARE.SESSION.STORE.DBI:DBI-STORE :CONNECTOR #<FUNCTION (LAMBDA NIL :IN "/mnt/Data/C..
  2: ((LAMBDA (LACK.MIDDLEWARE.SESSION::ENV) :IN "/mnt/Data/Code/endsec/end-world/ql-world-2017-08/software/lack-20170830-git/src/middleware/session.lisp") (:REQUEST-METHOD :GET :SCRIPT-NAME "" :PATH-INFO ..
  3: (LACK.UTIL:FUNCALL-WITH-CB #<CLOSURE (LAMBDA (LACK.MIDDLEWARE.SESSION::ENV) :IN "/mnt/Data/Code/endsec/end-world/ql-world-2017-08/software/lack-20170830-git/src/middleware/session.lisp") {10089A483B}>..
  4: ((LAMBDA (LACK.MIDDLEWARE.BACKTRACE::ENV) :IN "/mnt/Data/Code/endsec/end-world/ql-world-2017-08/software/lack-20170830-git/src/middleware/backtrace.lisp") (:REQUEST-METHOD :GET :SCRIPT-NAME "" :PATH-I..
  5: ((:METHOD HUNCHENTOOT:ACCEPTOR-DISPATCH-REQUEST (CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR T)) #<CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR (host *, port 5000)> #<HUNCHENTOOT:REQUEST {10035934D3}>) [fa..
  6: ((:METHOD HUNCHENTOOT:HANDLE-REQUEST (HUNCHENTOOT:ACCEPTOR HUNCHENTOOT:REQUEST)) #<CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR (host *, port 5000)> #<HUNCHENTOOT:REQUEST {10035934D3}>) [fast-method]
  7: ((:METHOD HUNCHENTOOT:PROCESS-REQUEST (T)) #<HUNCHENTOOT:REQUEST {10035934D3}>) [fast-method]
  8: (HUNCHENTOOT::DO-WITH-ACCEPTOR-REQUEST-COUNT-INCREMENTED #<CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR (host *, port 5000)> #<CLOSURE (LAMBDA NIL :IN HUNCHENTOOT:PROCESS-CONNECTION) {100359288B}>)
  9: ((:METHOD HUNCHENTOOT:PROCESS-CONNECTION (HUNCHENTOOT:ACCEPTOR T)) #<CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR (host *, port 5000)> #<USOCKET:STREAM-USOCKET {1001DD7AE3}>) [fast-method]
 10: ((:METHOD HUNCHENTOOT:PROCESS-CONNECTION :AROUND (HUNCHENTOOT:ACCEPTOR T)) #<CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR (host *, port 5000)> #<USOCKET:STREAM-USOCKET {1001DD7AE3}>) [fast-method]
 11: ((:METHOD HUNCHENTOOT:PROCESS-CONNECTION :AROUND (CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR T)) #<CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR (host *, port 5000)> #<USOCKET:STREAM-USOCKET {1001DD7AE3}>)..
 12: ((FLET HUNCHENTOOT::PROCESS-CONNECTION% :IN HUNCHENTOOT::HANDLE-INCOMING-CONNECTION%) #<CLACK.HANDLER.HUNCHENTOOT::CLACK-ACCEPTOR (host *, port 5000)> #<USOCKET:STREAM-USOCKET {1001DD7AE3}>)
 13: ((LAMBDA NIL :IN BORDEAUX-THREADS::BINDING-DEFAULT-SPECIALS))
 14: ((FLET "WITHOUT-INTERRUPTS-BODY-4" :IN SB-THREAD::INITIAL-THREAD-FUNCTION-TRAMPOLINE))
 15: ((FLET SB-THREAD::WITH-MUTEX-THUNK :IN SB-THREAD::INITIAL-THREAD-FUNCTION-TRAMPOLINE))
 16: ((FLET "WITHOUT-INTERRUPTS-BODY-1" :IN SB-THREAD::CALL-WITH-MUTEX))
 17: (SB-THREAD::CALL-WITH-MUTEX #<CLOSURE (FLET SB-THREAD::WITH-MUTEX-THUNK :IN SB-THREAD::INITIAL-THREAD-FUNCTION-TRAMPOLINE) {7FFFEF50ED5B}> #<SB-THREAD:MUTEX "thread result lock" owner: #<SB-THREAD:THR..
 18: (SB-THREAD::INITIAL-THREAD-FUNCTION-TRAMPOLINE #<SB-THREAD:THREAD "hunchentoot-worker-127.0.0.1:51360" RUNNING {1001DE5113}> NIL #<CLOSURE (LAMBDA NIL :IN BORDEAUX-THREADS::BINDING-DEFAULT-SPECIALS) {..
 19: ("foreign function: call_into_lisp")
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