Re: Some indexing advice for a Postgres newbie, please?

On Thu, 19 Feb 2015 09:30:57 -0700, you wrote:

>On 02/19/2015 09:10 AM, brian wrote:
>> Hi folks,
>>
>> I have a single-user application which is growing beyond the
>> fixed-format data files in which it currently holds its data, I need a
>> proper database as the backend. The front end is written using Lazarus
>> and FreePascal under Linux, should anyone feel that makes a
>> difference. The database will need to grow to around 250,000 records.
>>
>> My problem is with the data field which is the (unique) key. It's
>> really a single 192-bit integer (it holds various bits of bitmapped
>> data) which I currently hold as six 32-bit integers, but can convert
>> if needed when transferring the data.
>>
>> How would you advise that I hold this field in a Postgres database,
>> given the requirement for the whole thing to be a unique key? The
>> first 64 bits change relatively infrequently, the last 128 bits will
>> change with virtually every record. The last 128 bits will ALMOST be
>> unique in themselves, but not quite. :(
>>
>> Thanks,
>>
>> Brian.
>>
>>
>If your application understands/parses/makes use of the data in those
>192 bites, I would reload with an additional unique id field. For the
>intended number of rows of data a sequence would be fine, though I'm
>partial to UUIDs. Alternatively map the 192 bytes to two fields and make
>a unique key of both of them. Third alternative would be to use a binary
>BitString a suggested by Brian.

Thanks. The purpose of the field is purely as a check against the user
feeding the same data in twice. Once I've constructed it, I never pull
the field apart again. It had to be done this way, as otherwise the
boolean statement to check for uniqueness was horrendous.

Brian.