The segmentation is generally done on a primary key column. Vertica uses a particular hash segmentation method to segment data of tables among nodes.
More about optimizing GROUP BY can be found here: Īs discussed earlier, Projections may be stored among nodes of a cluster in a segmented or unsegmented way. Sorting also helps to speed up GROUP BY, if yourĬolumns are sorted in the same way as your GROUP BY condition, the query More about the different join algorithms used in Little memory and speeds up your query several times, especially when Presorted joinĬolumns use a faster join technique called Merge Joins which uses very
#Vertica dbvisualizer how to
How to stop this? Sort the columns in the JOIN condition. Massive query that does a lot of HASH joins on several tables with lots Not just the query that you areĬurrently executing, but the whole cluster could be slowed down by a More than the size of the memory available, disk paging starts and your It isĮxpensive because a hash is created in the memory using the join keys of Same way or if there is an inequality condition in the join. Sees that the columns on which the join are happening aren't sorted the Hash join is an algorithm used by Vertica for joining two tables when it More about Explain PLAN Output in Vertica can be found at Īs you take a closer look you come across two prime suspects: What you spot there is what you have to work on.īut how do I deal with what I spot in explain plan? How do we write Query Specific projections?įirst thing is to check out the query plan of our problematic query. Sometimes to get the best performance we have to write query specific projections. We can make modifications to these projections manually or run the Database Designer to generate projections for us. Stored in projections which are stored among nodes in various waysĭepending on the K Safety and the Segmentation options that we choose In Vertica even though we access data through tables everything is I thought I'd share some of the things that I did to improve my query performance. Hey there, I guess you have been having a lot fun with your Vertica databases.
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