Hi all,
I'm a beginner when it comes to Postgresql, and have a table design question about a project I'm currently working on. I have 1500 data items that need to be copied every minute from an
external system into my database. The items have a timestamp, an
identifier and a value. For example:
12/10/2008 05:00 ID_ABC 14
12/10/2008 05:01 ID_ABC 17
12/10/2008 05:02 ID_ABC 13
Pretty simple stuff. The current solution (implemented using SQL Server a few years ago) looks like this (an approximation using Postgresql syntax):
CREATE TABLE "DataImport"
(
"DataImportID" serial NOT NULL PRIMARY KEY,
"Time" timestamp without time zone NOT NULL,
"ID_ABC" integer NOT NULL,
"ID_DEF" integer NOT NULL,
"ID_HIJ" integer NOT NULL,
etc
);
While this design results in only 14400 records being present in the table per day, I don't like it. One problem is that every time a data item is added or removed from the import process, the structure of the table needs to be altered. I don't know what sort of overhead that involves in the Postgresql world, but I'm thinking that once I define the structure of the table, I don't want to be messing with it very often, if at all.
My initial thought for the design of the new solution looks like this:
CREATE TABLE "DataImport"
(
"DataImportID" serial NOT NULL PRIMARY KEY,
"Time" timestamp without time zone NOT NULL,
"Identifier" text NOT NULL,
"Value" integer NOT NULL
);
Users will then be doing regular queries on this data (say, a few hundred times per day), such as:
SELECT "Time", "Value" FROM "DataImport" WHERE "Identifier" = 'ID_ABC' AND "Time" between '2008-11-07' and '2008-11-11';
My concern is that 1500 values * 14400 minutes per day = 21,600,000 records. Add this up over the course of a month (the length of time I need to keep the data in this table) and I'll have more than half a billion records being stored in there.
I guess my question is: is my approach reasonable? I haven't dealt with tables of this size before (using any DBMS) - should I expect really slow queries due to the sheer number of records present? Is there some better way I should be structuring my imported data? All suggestions welcome.
Cheers,
Andrew
