From: Carsten Gehling <carsten@...>
Date: 2009-09-15T13:29:16+09:00
Subject: Re: Pre-allocate large amount of memory?

Robert Klemme wrote:

> Is your structure strictly hierarchical (i.e. a tree) or do you need to
> query part of a graph with cycles?  If it is strictly hierarchical there
> is a solution that works for all RDBMS and in the latter case there are
> solutions for some RDBMS.

Unfortunately it is not strictly hierarchial. It is relations between 
companies-companies and companies-persons, that represents shareholders, 
parent-/subsidiary companies, etc.

My job is to - given a certain company X - to extract all its owners 
and, recursively, their owners, etc. until I reach the "top". Likewise 
the other way to extract all companies owned by company X and, 
recursively, all companies owned by them, etc.

Conceptually, the table (actually a view) I am querying holds the data:

CompanyA,  Direction, CompanyB,  Share
"FooCorp", "owns",    "BarCorp", "10%"
"BarCorp", "ownedby", "FooCorp", "10%"
"BarCorp", "owns",    "BazCorp", "45%"
"BasCorp", "ownedby", "BarCorp", "45%"
"QweCorp", "owns",    "RteCorp", "20%"
"RteCorp", "ownedby", "QweCorp", "20%"
etc.

The table is not of my doing. It is very difficult (at least for me) to 
devise a way to only query the nessecery rows in the table, without 
sorting to recursive calls.

In the example above: If given "FooCorp", all but the last two rows 
should be extracted and used in the result. How would you go about doing 
that?

I haven't found a solution yet. This is why I've gone and made a 
service, that holds all these data in memory (in a hash), to speed up on 
things.

BTW: Thanks for all your great suggestions so far. :-)

- Carsten
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