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List:       postgresql-general
Subject:    [HACKERS] Major Feature Interactions
From:       "Simon Riggs" <simon () 2ndquadrant ! com>
Date:       2007-02-28 13:10:28
Message-ID: 1172668229.3760.958.camel () silverbirch ! site
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There's a number of major features all coming together over the next
weeks, so I wanted to raise some awareness of possible areas of
interaction. My concern is more than just "will multiple patches apply
together?", but extends into whether the features interact with each
other with synergy, ignore each other or have negative impact.

The projects that concern me are the following internals projects

Plan Invalidation
Autovacuum changes
Bitmap indexes
GIT indexes
Dead Space Map (DSM)
HOT Updating
Updateable cursors
Restartable VACUUM

The potential interactions as I understand them are these: I'm not
saying this list is either complete or accurate; checking whether it is
or not is exactly the reason for this post.

Anyway, just trying to raise awareness to look for potential issues.

UpdCursors
----------
	Syntax changes only, no impact on other projects mentioned.

HOT
---
GIT
	Used to be some conflicts at patch level, now gone?
	Positive impact on GIT performance
PlanInval
	heap_check_hotupdate() test can performed in planner, so
	will no longer be a heap function
DSM
	HOT updates need not be logged, since they will be cleared
	by retail VACUUMs
BitmapIdx
	Potential issue with chilling tuples during CREATE INDEX
AutoVac
	HOT will change how UPDATEs are reported to pg_stat, by
	adding additional fields.
UpdCursors
	Should tidscan follow chain to correct tuple? That seems to
	change current behaviour even if it might be useful.
	
Plan Invalidation
-----------------
	No known changes, other than the integrations already mentioned

Autovacuum changes
------------------
DSM
	Is implementing new forms of VACUUM: VACUUM and VACUUM ALL.
	Does reporting of row stats change? 

Bitmap indexes
--------------
GIT
	Do we need both? I think yes, but need to see some info on
	when crossover occurs between two index methods.

Restartable VACUUM
------------------
DSM
	Interactions with DSM?
HOT
	Must use full cycles only

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com



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