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When your projection is not cost-free
First of all I have to admit that the title of this post is a bit misleading - the projection is almost never "cost-free". Indirectly cost will be generated by accessing rows from row sources to obtain...
View ArticleExadata Smart Scan Projection Limitation
Here is an interesting limitation to Exadata Smart Scans - if more than 254 columns from a table (not HCC compressed, more on that in moment) need to be projected, Smart Scans for that particular...
View ArticleParallel Projection
A recent case at a client reminded me of something that isn't really new but not so well known - Oracle by default performs evaluation at the latest possible point in the execution plan.So if you...
View ArticleDynamoDB: adding a Global covering index to reduce the cost
By Franck Pachot. People often think of indexes as a way to optimize row filtering (“get item” faster and cheaper). But indexes are also about columns (“attribute projection”) like some kind of...
View ArticleDynamoDB: adding a Local covering index to reduce the cost
By Franck Pachot. This is a continuation on the previous post on DynamoDB: adding a Global Covering Index to reduce the cost. I have a DynamoDB partitioned on “MyKeyPart”,”MyKeySort” and I have many...
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