Re: Fwd: Re: Can I search for an array in csf? - Mailing list pgsql-sql

Hi, Achilleus and Josh,

I know three ways to store dynamic array in DB: object, xml or csv, and sub-table. It seems to me there are some 
problems of using the first method in Java. I don't know how the third method work out. That is the reason I use the 
second method.

In my project, the simplest array type is an array of characters or user IDs. The complexest array is an array of data
type
 
of userid and another text field. All operations on the arrays are simple: either element look up, add or delete an
element.
 
Which method is the most suitable for those different operations.

Thanks very much for all your helps.

Vernon


Thanks for your information. See below.

10/22/2002 1:03:56 AM, Achilleus Mantzios <achill@matrix.gatewaynet.com> wrote:

>On Mon, 21 Oct 2002, Josh Berkus wrote:
>
>>
>> Vernon,
>>
>> > >> One field of a table stores an array of characters in a string fromat as
>> > >> "a,b,c,d". Is anyway to apply a select statement without using stored
>> > >> procedure?
>>
>> > The reason I use this format for an array is that the array is dynamic. I
>> have quite few cases of this type of situation. The
>> > maximize length in some cases is known, is unknown in others. I have learnt
>> the comment separated format is one way
>> > to solve the problem. Someone also suggested to store the array as an
>> object. I am not sure whether it works or not.
>> > The application is written in Java, by the way.
>>
>> You should store this data in a sub-table linked through a foriegn key.
>> Period.   Messing with arrays will only lead you to heartache ...
>
>It depends.
>I can tell you of situations that doing it with child tables
>will hurt performance really bad.
>Its just a matter of complexity.
>
>One of the apps we run over here, deals with bunker
>analysis of the vessels of our fleet.
>
>For each vessel there are 4 formulas that describe the parameters of
>the consumption of fuel oil under some given conditions.
>
>I have implemented this using arrays.
>The app is written in J2EE.
>
>On a dual xeon 2.2 GHz with 1 GB for postgres,
>it takes about 900 miliseconds to compute
>some statistics (average, std deviation,etc..)
>of the consumption of all vessels (about 20 of them)
>for a period of 3 years (the values are stored for each day).
>
>Before going with the formulas, we had a rather
>primitive scheme originated from the previous
>cobol application, based on subtable look ups,
>(and there was no serious computations involved
>just table lookups).
>
>I can tell you the performance boost was remarkable.
>
>>
>> Try the book "Database Design For Mere Mortals" for a primer on SQL DB design.
>>
>> --
>> -Josh Berkus
>>  Aglio Database Solutions
>>  San Francisco
>>
>>
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>
>==================================================================
>Achilleus Mantzios
>S/W Engineer
>IT dept
>Dynacom Tankers Mngmt
>Nikis 4, Glyfada
>Athens 16610
>Greece
>tel:    +30-10-8981112
>fax:    +30-10-8981877
>email:  achill@matrix.gatewaynet.com
>        mantzios@softlab.ece.ntua.gr
>
>