"carter ck" <carterck32@xxxxxxxxxxx> writes: > I am wonderring the differences between creating an index on several columns > of a table and an index on each column of a table. > For example, following is my select query: > select * from my_table where myrowid='abc' and mytask='TEst 1' and > myday!='holiday'; > Which of the following is a correct way of indexing the column? > 1. create index my_table_my_index on my_table(myrowid, mytask, myday); > 2. i. create index my_table_myrow_index on my_table(myrowid); > ii. create index my_table_mytask_index on my_table(mytask); > iii. create index my_table_myday_index on my_table(myday); The not-equal condition is not indexable, so you can disregard that. If this specific query is all you care about then a two-column index on (myrowid, mytask) is the best bet, but if you have a mix of queries involving one or both columns then two separate indexes might be better. See http://www.postgresql.org/docs/8.2/static/indexes.html particularly sections 11.3 and 11.4, and don't be afraid to experiment. regards, tom lane
