I have two possible queries, both giving the result set I want.
Query one takes about 30ms, but 150ms to fetch the data from the database.
SELECT
id
FROM
featurevalues as featval3
WHERE
featval3.feature IN (?,?,?,?)
AND
EXISTS
(
SELECT
1
FROM
product_to_value,
product_to_value as prod2,
features,
featurevalues
WHERE
product_to_value.feature = features.int
AND
product_to_value.value = featurevalues.id
AND
features.id = ?
AND
featurevalues.id IN (?,?)
AND
product_to_value.product = prod2.product
AND
prod2.value = featval3.id
)
Query two takes about 3ms -this is the one I therefore prefer-, but also takes 170ms to fetch the data.
SELECT
(
SELECT
prod2.value
FROM
product_to_value,
product_to_value as prod2,
features,
featurevalues
WHERE
product_to_value.feature = features.int
AND
product_to_value.value = featurevalues.id
AND
features.id = ?
AND
featurevalues.id IN (?,?)
AND
product_to_value.product = prod2.product
AND
prod2.value = featval3.id
) as id
FROM
featurevalues as featval3
WHERE
featval3.feature IN (?,?,?,?)
The 170ms seems to be related to the number of rows from table featval3. After an index is used on featval3.feature IN (?,?,?,?), 151 items "remain" in featval3.
Is there something obvious I am missing regarding the slow fetching? As far as I know everything is properly indexed.. I am confused because the second query only takes a blazing 3ms to run.
Update
This is what i get when I'm running an EXPLAIN on the second query:
0 Trace 0 0 0 00
1 Variable 4 1 4 00
2 Goto 0 88 0 00
3 OpenRead 5 6883 0 00
4 If 6 16 0 00
5 Integer 1 6 0 00
6 OpenEphemeral 7 1 0 00
7 Null 0 8 0 00
8 MakeRecord 1 1 8 00
9 IdxInsert 7 8 0 00
10 MakeRecord 2 1 8 00
11 IdxInsert 7 8 0 00
12 MakeRecord 3 1 8 00
13 IdxInsert 7 8 0 00
14 MakeRecord 4 1 8 00
15 IdxInsert 7 8 0 00
16 Rewind 7 86 0 00
17 Column 7 0 5 00
18 IsNull 5 85 0 00
19 Affinity 5 1 0 00
20 SeekGe 5 85 5 00
21 IdxGE 5 85 5 01
22 Null 0 10 0 00
23 Integer 1 11 0 00
24 MustBeInt 11 0 0 00
25 IfZero 11 82 0 00
26 Variable 1 12 3 00
27 OpenRead 2 25 0 00
28 OpenRead 8 7005 0 00
29 OpenRead 9 26 0 00
30 OpenRead 10 6732 0 00
31 OpenRead 11 6766 0 00
32 Column 5 1 15 00
33 IsNull 15 77 0 00
34 Affinity 15 1 0 00
35 SeekGe 8 77 15 00
36 IdxGE 8 77 15 01
37 IdxRowid 8 8 0 00
38 Seek 2 8 0 00
39 Column 2 0 16 00
40 IsNull 16 76 0 00
41 Affinity 16 1 0 00
42 SeekGe 9 76 16 00
43 IdxGE 9 76 16 01
44 Column 9 1 17 00
45 IsNull 17 75 0 00
46 SCopy 12 18 0 00
47 IsNull 18 75 0 00
48 Affinity 17 2 0 00
49 SeekGe 10 75 17 00
50 IdxGE 10 75 17 01
51 If 20 59 0 00
52 Integer 1 20 0 00
53 OpenEphemeral 13 1 0 00
54 Null 0 21 0 00
55 MakeRecord 13 1 21 00
56 IdxInsert 13 21 0 00
57 MakeRecord 14 1 21 00
58 IdxInsert 13 21 0 00
59 Rewind 13 74 0 00
60 Column 13 0 19 00
61 IsNull 19 73 0 00
62 Affinity 19 1 0 00
63 SeekGe 11 73 19 00
64 IdxGE 11 73 19 01
65 Column 9 2 21 00
66 Column 11 0 7 00
67 Ne 7 72 21 6a
68 Column 8 0 22 00
69 Move 22 10 1 00
70 AddImm 11 -1 0 00
71 IfZero 11 77 0 00
72 Next 11 64 0 00
73 Next 13 60 0 00
74 Next 10 50 0 00
75 Next 9 43 0 00
76 Next 8 36 0 00
77 Close 2 0 0 00
78 Close 8 0 0 00
79 Close 9 0 0 00
80 Close 10 0 0 00
81 Close 11 0 0 00
82 SCopy 10 9 0 00
83 ResultRow 9 1 0 00
84 Next 5 21 0 00
85 Next 7 17 0 00
86 Close 5 0 0 00
87 Halt 0 0 0 00
88 Transaction 0 0 0 00
89 VerifyCookie 0 319 0 00
90 TableLock 0 14 0 00
91 TableLock 0 25 0 00
92 TableLock 0 11 0 00
93 Goto 0 3 0 00
Not sure what it means however.