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Delete Costs

One of the quirky little anomalies of the optimizer is that it’s not allowed to select rows from a table after doing an index fast full scan (index_ffs) even if it is obviously the most efficient (or, perhaps, least inefficient) strategy. For example:

Delete Costs

One of the quirky little anomalies of the optimizer is that it’s not allowed to select rows from a table after doing an index fast full scan (index_ffs) even if it is obviously the most efficient (or, perhaps, least inefficient) strategy. For example:

Cluster Nulls

Yesterday’s posting was a reminder that bitmap indexes, unlike B-tree indexes in Oracle,  do store entries where every column in the index is null. The same is true for cluster indexes – which are implemented as basic B-tree indexes. Here’s a test case I wrote to demonstrate the point.

Cluster Nulls

Yesterday’s posting was a reminder that bitmap indexes, unlike B-tree indexes in Oracle,  do store entries where every column in the index is null. The same is true for cluster indexes – which are implemented as basic B-tree indexes. Here’s a test case I wrote to demonstrate the point.

BGOUG Spring 2014 : Summary

I know I keep calling it the “spring” conference, but in my mind the two BGOUG conferences are always spring and autumn. This year the “spring” conference was a little late, hence my apparently strange blog titles. :)

I was initially planning to get a taxi from Sandanski to Sofia airport. Fortunately Sve and Mimi were driving back at the same time, so I got a lift with them, which was much better company.

The flight from Sofia to Munich went as planned. After a 110 minute layover in Munich, it was time for the last leg of the journey to Birmingham. Once again, so drama there.

Execution Plans

This is the index to a series of articles I’ve been writing for redgate, published on their AllThingsOracle site, about generating and reading execution plans. I’ve completed a few articles that haven’t yet been published, but I’ll add their URLs when they’re available.

I don’t really know how many parts it’s going to end up as – there’s an awful lot that that you could say about reading execution plans, even when you’re trying to cover just the basics; every time I’ve started writing an episode in the series it’s turned into two episodes.  I’ve delivered 5 parts to redgate so far; the active URLs below are the ones that they are currently online.

Bitmap Nulls

It’s fairly well known that in Oracle B-tree indexes on heap tables don’t hold entries where all the indexed columns are all null, but that bitmap indexes will hold such entries and execution plans can for predicates like “column is null” can use bitmap indexes. Here’s a little test case to demonstrate the point (I ran this last on 12.1.0.1):

Bitmap Nulls

It’s fairly well known that in Oracle B-tree indexes on heap tables don’t hold entries where all the indexed columns are all null, but that bitmap indexes will hold such entries and execution plans can for predicates like “column is null” can use bitmap indexes. Here’s a little test case to demonstrate the point (I ran this last on 12.1.0.1):

BGOUG Spring 2014 – Day 2

The Day 1 evening festivities consisted of lots of food, followed by a group doing a display of traditional dances. Once they had finished it was up to me to teach the Bulgarians how their local dances should really be done. Needless to say I smashed it! :)

Day 2 started with a swim and breakfast. When I say swim, I really mean gentle floating, wishing I was still in bed.

The first session I went to was Joel Goodman‘s session on “RAC Global Resource Management”. Lot’s of good stuff! Joel is like a walking Oracle encyclopedia.

EM12c Release 4, Private Roles

Until OEM11g, it was very common that all folks were either Super Administrators or Administrators and only a few shops took the time to create roles outside of these two essential roles.  Super Administrator, (SA) was pretty straight forward-  the SA had essentially the same access as the repository owner and should only be allocated to those that should have this deep access to the Enterprise Manager environment, but admi