SQL SELECT speed int vs varchar

Some rough benchmarks:

4 million records in Postgres 9.x

Table A = base table with some columns
Table B = Table A + extra column id of type bigint with random numbers
Table C = Table A + extra column id of type text with random 16-char ASCII strings

Results on 8GB RAM, i7, SSD laptop:

Size on disk:                A=261MB        B=292MB        C=322MB
Non-indexed by id: select count(*), select by id: 450ms same on all tables
Insert* one row per TX:       B=9ms/record        C=9ms/record
Bulk insert* in single TX:    B=140usec/record    C=180usec/record
Indexed by id, select by id:  B=about 200us       C=about 200us

* inserts to the table already containing 4M records

so it looks like for this setup, as long as your indexes fit in RAM, bigint vs 16-char text makes no difference in speed.

Int comparisons are faster than varchar comparisons, for the simple fact that ints take up much less space than varchars.

This holds true both for unindexed and indexed access. The fastest way to go is an indexed int column.

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As I see you've tagged the question postgreql, you might be interested in the space usage of different date types:

• int fields occupy between 2 and 8 bytes, with 4 being usually more than enough ( -2147483648 to +2147483647 )
• character types occupy 4 bytes plus the actual strings.