On Fri, Apr 17, 2015 at 8:45 AM, Melvin Davidson <melvin6...@gmail.com> wrote:
> > On Fri, Apr 17, 2015 at 11:34 AM, Kynn Jones <kyn...@gmail.com> wrote: > >> >> One consideration that is complication the choice of primary key >> is wanting to have the ability to store chunks of the data >> table (not the metadata table), including the PK column, as >> matrices of doubles. In its simplest form, this would mean using >> doubles as primary keys, but this seems to me a bit weird. >> >> I'm willing to go ahead with this, but I wanted to ask for your >> feedback on the whole thing. In particular I'd like to know if >> there are there standard ways for using doubles as primary keys, >> and, conversely, if there are known pitfalls I should be looking >> out for, but I welcome any other words of wisdom you may have on >> this topic. >> > MD>> First, please ALWAYS include the version and O/S, even with basic questions. MD>> I'm not sure what you mean by doubles. Do you mean bigint data type, or do you mean use two columns for a primary key? Either way it's pretty simple. MD>> If you mean a bigint, then probably best to use serial data type, which will default to the next value. MD>> If you mean use two columns for a Primary Key, the you just specify the columns. MD>> EG: CONSTRAINT PRIMARY KEY table_name_pk PRIMARY KEY (col1, col2) I take it the OP means "double precision" http://www.postgresql.org/docs/9.0/static/datatype-numeric.html I'd be suspect of choosing a PK whose type definition includes the word "inexact". You also say you want to store the data as a double precision but you never actually explain what the natural key of the data is. If you are strictly storing serial (big) integers but doing so within a double precision typed column you may be OK - but I would advise taking input from someone with more expertise on the properties of IEEE floating point numbers. David J.
