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.
根据SO-ers的建议,我将一个MS Access数据库(由于测试原因,一个小数据库)转换为SQLite。它有两个表,一个有5k个条目,另一个有50k个条目。
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.
现在,我将在QuLimma和QLexeis下面的查询使用Access花费大约60ms(下面函数的总时间),但是使用SQLite需要大约830ms。
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:
使用连接字符串:
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.
现在,在有人问“不是60ms足够快?”之前,我想说我这样做是因为我有其他Access文件和查询需要3-4秒才想降低它们,所以是的,我希望在这一个中从60ms降到30或更低。
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.
我是否存在配置错误,或者仅仅是SQLite不是更快?我已经检查过,两者都返回正确的结果,没有奇怪的循环问题。
Edit: most of the time is consumed by the second query.
编辑:大部分时间由第二个查询消耗。
Edit 2: (copy/paste from the db.sql)
编辑2 :(从db.sql复制/粘贴)
Table Limma:
表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
总计:64k条目
Table Words:
表格词:
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
总计:6k条目
The first field "id" is unique.
第一个字段“id”是唯一的。
6
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.
您几乎不想在可以使用WHERE标准的地方使用HAVING。您正在评估所有可能的结果,然后在聚合后将其剔除。您主要想要根据汇总结果使用HAVING标准。在这种情况下,通过在聚合之前将HAVING逻辑移动到WHERE条件,可以实现相同的目的。这应该会大大加快您的查询速度。
There is also no need to use GROUP BY logic since you're not returning any aggregates, just use DISTINCT.
也没有必要使用GROUP BY逻辑,因为您没有返回任何聚合,只需使用DISTINCT。
I would write it like this:
我会这样写:
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:
对于具有表模式的这两个查询,这些索引应优化查询:
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.
请记住,在插入每个附加索引时都会有成本。您必须权衡此成本与指数的好处。如果您的表包含静态数据,那么没有任何损害。