Hi!
I don't think I would go as far as saying multiple trees is a good
solution, I know from studying the commercial vendors that they tend
to have just one/maybe two trees but the concept I believe is right. A
lot of the reasons most databases have these is because they didn't
begin with an SQL interface (or banked on being able to support
multiple languages in the beginning).
MySQL only had one tree type, which was Item. It is not very
serializable and is not re-entrant. The lack of being re-entrant is
one of the bigger flaws I currently see in it, and one of the base
problems I would like to see solved in a new version.
Cheers,
-Brian
On May 4, 2009, at 10:50 AM, Alex Esterkin wrote:
I think the root of the problem is that MySQL lacks separation of
concerns: the same parse tree is used at every stage of query
processing. On the other hand, in Postgres, a parse tree is
represented by a Query structure (a tree of C structures), the query
optimizer generates and considers a bunch of throwaway Path tree
structures, then the query planner generates a tree of Plan nodes
(Plan tree). The query execution is a state machine; Init...(_)
functions generate various PlannerInfo structures/nodes, which are
ultimately responsible for runtime query execution. In the Postgres
world, only Query tree and Plan tree need to be copyable and
serializable. This makes everything simpler.
Regards,
Alex Esterkin
On Mon, May 4, 2009 at 1:05 PM, Brian Aker <[email protected]> wrote:
Hi!
On May 4, 2009, at 9:22 AM, Jim Starkey wrote:
that uses parameters, reducing the threat of SQL insertion. I don't
think, however, that it is feasible as a plugin.
The big issue here is having some sort of parse tree that is
serialize'able. Once you have that it is a matter of some protocol
plugin being able to push a piece of execution into the "right"
point in the stack.
Refactoring ITEM into something which is useable/revisionable/etc...
seems to be the key.
Cheers,
-Brian
--
_______________________________________________________
Brian "Krow" Aker, brian at tangent.org
Seattle, Washington
http://krow.net/ <-- Me
http://tangent.org/ <-- Software
_______________________________________________________
You can't grep a dead tree.
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