Good afternoon, tell me, please, what is the SARG argument and how does the optimizer use it?
0xdb
one
Nick Proskuryakov Nick Proskuryakov
2,673 1 golden mark 7 silver marks 29 bronze marks
|
1 answer
SARG = Seekable ARGument, an argument that, when inserted into the WHERE allows you to use an index. For example:
SELECT * FROM myTable WHERE id = 3; can use the index on the id field, but:
SELECT * FROM myTable WHERE (id * 3) = 3; no, because you need to multiply each value of id in the table, which is equivalent to complete enumeration. NonSARG can greatly slow down the execution of your queries, especially often such arguments are obtained as a result of casting tuple values to another type.
Mirdin mirdin
5.672 1 golden mark 17 silver marks 29 bronze marks
- It seems to be a Search Argument, so it is an internal parameter (since it is not visible SAGR query or NonSARG) optimizer to determine the possibility of using the index? - Nick Proskuryakov
- @ WizarD51 1. Search / Seek - synonyms :) 2. For NonSARG, the optimizer simply cannot use the index. Or I do not understand your difficulties? - Mirdin
- Everything is ok, thanks) - Nick Proskuryakov
|