[pyar] OT: Comparación de queries

[Sebastian Bassi]

2010/6/20 Roberto Alsina <ralsina en netmanagers.com.ar>:
> Tal vez sea buena idea pedir un EXPLAIN para ver que hace cada una.

Buena idea, no entiendo bien el output pero se ve que la equi-join se
hacen en menos pasos:

sqlite> EXPLAIN SELECT q_name FROM miranda WHERE parID in (SELECT
parID FROM parid_bin WHERE bin = '10B');
0|Trace|0|0|0|EXPLAIN SELECT q_name FROM miranda WHERE parID in
(SELECT parID FROM parid_bin WHERE bin = '10B');|00|
1|Goto|0|28|0||00|
2|SetNumColumns|0|2|0||00|
3|OpenRead|0|86|0||00|
4|If|2|18|0||00|
5|Integer|1|2|0||00|
6|OpenEphemeral|3|1|0|keyinfo(1,BINARY)|00|
7|String8|0|3|0|10B|00|
8|SetNumColumns|0|2|0||00|
9|OpenRead|1|1286|0||00|
10|Rewind|1|17|0||00|
11|Column|1|1|4||00|
12|Ne|3|16|4|collseq(BINARY)|69|
13|Column|1|0|6||00|
14|MakeRecord|6|1|4|c|00|
15|IdxInsert|3|4|0||00|
16|Next|1|11|0||01|
17|Close|1|0|0||00|
18|Rewind|3|26|0||00|
19|Column|3|0|1||00|
20|IsNull|1|25|0||00|
21|MustBeInt|1|25|0||00|
22|NotExists|0|25|1||00|
23|Column|0|1|7||00|
24|ResultRow|7|1|0||00|
25|Next|3|19|0||00|
26|Close|0|0|0||00|
27|Halt|0|0|0||00|
28|Transaction|0|0|0||00|
29|VerifyCookie|0|38|0||00|
30|TableLock|0|86|0|miranda|00|
31|TableLock|0|1286|0|parid_bin|00|
32|Goto|0|2|0||00|
sqlite> EXPLAIN SELECT q_name FROM miranda,parid_bin WHERE
miranda.parID=parid_bin.parID AND parid_bin.bin = '10B';
0|Trace|0|0|0|EXPLAIN SELECT q_name FROM miranda,parid_bin WHERE
miranda.parID=parid_bin.parID AND parid_bin.bin = '10B';|00|
1|String8|0|1|0|10B|00|
2|Goto|0|19|0||00|
3|SetNumColumns|0|2|0||00|
4|OpenRead|1|1286|0||00|
5|SetNumColumns|0|2|0||00|
6|OpenRead|0|86|0||00|
7|Rewind|1|16|0||00|
8|Column|1|1|2||00|
9|Ne|1|15|2|collseq(BINARY)|69|
10|Column|1|0|2||00|
11|MustBeInt|2|15|0||00|
12|NotExists|0|15|2||00|
13|Column|0|1|4||00|
14|ResultRow|4|1|0||00|
15|Next|1|8|0||01|
16|Close|1|0|0||00|
17|Close|0|0|0||00|
18|Halt|0|0|0||00|
19|Transaction|0|0|0||00|
20|VerifyCookie|0|38|0||00|
21|TableLock|0|1286|0|parid_bin|00|
22|TableLock|0|86|0|miranda|00|
23|Goto|0|3|0||00|


-- 
Sebastián Bassi. Lic. en Biotecnologia.

Curso de Python en un día: http://bit.ly/cursopython

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