SQLite terribly slow compared to MS Access - sql

Question

Following the advice of fellow SO-ers, I converted an MS Access database I had (a small one, for test reasons) to SQLite. It has two tables, one with 5k entries and another with 50k entries.
Now, the queries I will present below QuLimma and QLexeis took about 60ms (total time of the function below) with Access, but a whopping 830ms with SQLite.
Dim i As Integer
Dim ms As Integer
ResultPin(0) = ""
ResultPin(1) = ""
ResultPin(2) = ""
ResultPin(3) = ""
ResultPin(4) = ""
i = 0
Multichoice = 0
ms = 0
Dim rsTblEntries As ADODB.Recordset
Set rsTblEntries = New ADODB.Recordset
Dim QuLimma As String, QLexeis As String
QuLimma = "SELECT Words.limma, Words.limmabody, Words.limmapro " & _
"FROM Words " & _
"GROUP BY Words.limma, Words.limmabody, Words.limmapro " & _
"HAVING (((Words.limma)='" & StrLexeis & "'));"
QLexeis = "SELECT Limma.limmalexeis, Words.limma, Limma.limmabody, Words.limmapro, Limma.limmaexp " & _
"FROM Limma INNER JOIN Words ON Limma.limmabody = Words.limmabody " & _
"GROUP BY Limma.limmalexeis, Words.limma, Limma.limmabody, Words.limmapro, Limma.limmaexp " & _
"HAVING (((Limma.limmalexeis)='" & StrLexeis & "'));"
rsTblEntries.Open QuLimma, CnDataParSQLite ', adOpenStatic, adLockOptimistic
If rsTblEntries.EOF = True Then
rsTblEntries.Close
rsTblEntries.Open QLexeis, CnDataParSQLite ', adOpenStatic, adLockOptimistic
If rsTblEntries.EOF = True Then
SearchQParagSQLite = False
Else
SearchQParagSQLite = True
Do While rsTblEntries.EOF = False
ms = ms + 1
rsTblEntries.MoveNext
Loop
rsTblEntries.MoveFirst
If ms > 1 Then
Do While rsTblEntries.EOF = False
ResultTemp(0, i) = rsTblEntries.Fields("limma").Value & "" 'rsWordPar!limma
ResultTemp(1, i) = rsTblEntries.Fields("limmalexeis").Value & "" 'rsWordPar!limmalexeis
ResultTemp(2, i) = rsTblEntries.Fields("limmabody").Value 'rsWordPar!limmabody
If IsNull(rsTblEntries.Fields("limmapro").Value) = False Then ResultTemp(3, i) = rsTblEntries.Fields("limmapro").Value 'rsWordPar!limmapro
rsTblEntries.MoveNext
i = i + 1
Multichoice = 1
Loop
Else
Do While rsTblEntries.EOF = False
ResultPin(0) = rsTblEntries.Fields("limma").Value & "" 'rsWordPar!limma
ResultPin(1) = rsTblEntries.Fields("limmalexeis").Value & "" 'rsWordPar!limmalexeis
ResultPin(2) = rsTblEntries.Fields("limmabody").Value 'rsWordPar!limmabody
If IsNull(rsTblEntries.Fields("limmapro").Value) = False Then ResultPin(3) = rsTblEntries.Fields("limmapro").Value 'rsWordPar!limmapro
rsTblEntries.MoveNext
Multichoice = 0
Loop
End If
End If
Else
SearchQParagSQLite = True
rsTblEntries.MoveFirst
Do While rsTblEntries.EOF = False
ResultPin(0) = rsTblEntries.Fields("limma").Value & "" 'rsWordPar!limma
ResultPin(1) = "#"
ResultPin(2) = rsTblEntries.Fields("limmabody").Value 'rsWordPar!limmabody
If IsNull(rsTblEntries.Fields("limmapro").Value) = False Then ResultPin(3) = rsTblEntries.Fields("limmapro").Value 'rsWordPar!limmapro
rsTblEntries.MoveNext
i = i + 1
Loop
End If
i = 0
rsTblEntries.Close
Set rsTblEntries = Nothing
With connection string:
CnDataParSQLite.ConnectionString = "DRIVER=SQLite3 ODBC Driver;" & _
"Database=" & strDataPath & "u.sl3;LongNames=0;Timeout=1000;NoTXN=0;SyncPragma=NORMAL;StepAPI=0;"
CnDataParSQLite.Open
Now, before someone asks "wasn't 60ms fast enough?", I'd like to say that I did this because I have other Access files and queries which take 3-4 seconds and would like to lower them down, so yes, I was hoping to go down from 60ms to 30 or less in this one.
Do I have a misconfiguration or is it just that SQLite is not faster? I have checked, both return correct results, there is no weird looping issue.
Edit: most of the time is consumed by the second query.
Edit 2: (copy/paste from the db.sql)
Table Limma:
CREATE TABLE Limma ( id INTEGER PRIMARY KEY, limmabody INTEGER DEFAULT 0, limmalexeis VARCHAR2(100), limmastat VARCHAR2(50), limmaexp VARCHAR2(250));
INSERT INTO Limma VALUES (1, 1, 'υψικάμινος', 'ΣΠ', NULL);
INSERT INTO Limma VALUES (2, 1, 'υψίκορμος', 'ΣΠ', NULL);
INSERT INTO Limma VALUES (3, 1, 'υψίπεδο', 'ΑΠ', '<αρχ. υψίπεδον, ουδ. του επιθ. υψίπεδος<ύψι "ψηλά" + πέδον');
Total: 64k entries
Table Words:
CREATE TABLE Words ( id INTEGER PRIMARY KEY, limma VARCHAR2(100), limmabody INTEGER DEFAULT 0, limmapro VARCHAR2(200));
INSERT INTO Words VALUES (1, 'υψι (αχώριστο μόριο)', 1, NULL);
INSERT INTO Words VALUES (2, 'ομο (αχώριστο μόριο)', 2, NULL);
INSERT INTO Words VALUES (3, 'διχο (αχώριστο μόριο)', 3, NULL);
Total: 6k entries
The first field "id" is unique.

Answer 1

You almost never want to use HAVING where you can use WHERE criteria. You're evaluating all possible results and then culling them down after aggregation. You mainly want to use HAVING criteria where you're trying to cull down based upon the aggregated results. You can achieve the same thing by moving the HAVING logic to a WHERE criteria before the aggregation in this case. This should greatly speed up your query.
There is also no need to use GROUP BY logic since you're not returning any aggregates, just use DISTINCT.
I would write it like this:
QuLimma = "SELECT DISTINCT Words.limma, Words.limmabody, Words.limmapro " & _
"FROM Words " & _
"WHERE Words.limma ='" & StrLexeis & "';"
QLexeis = "SELECT DISTINCT Limma.limmalexeis, Words.limma, Limma.limmabody, Words.limmapro, Limma.limmaexp " & _
"FROM Limma INNER JOIN Words ON Limma.limmabody = Words.limmabody " & _
"WHERE Limma.limmalexeis ='" & StrLexeis & "';"
For these two queries with your table schema these indexes should optimize the queries:
CREATE NONCLUSTERED INDEX ix_words_1 ON Words (Limma) INCLUDE (Limmabody, Limmapro)
CREATE NONCLUSTERED INDEX ix_words_2 ON Words (Limmabody) INCLUDE (Limma, Limmapro)
CREATE NONCLUSTERED INDEX ix_limma_1 ON Limma (Limmabody, Limmalexeis) INCLUDE (Limmaexp)
Keep in mind there is a cost at the time of insert for each additional index you have. You have to weigh this cost against the benefit of the index. If your tables contain static data then there is no harm.