dc_tuple_mover_events / storage containers

Hi,
while running tests on how Vertica (11.1.1-17) behaves when being flooded with small transactions we used dc_tuple_mover_events to monitor TM actions.
Now I have some questions to this:
-1)What does the column container_count mean? The number of ROS per projection? The number of storage containers?
2) What is actually a storage container? The term is used quite frequently in the documentation, but I didn't find a definiton for it
3) When querying dc_tuple_mover_events I found that the value in container_count stays the same when comparing the "Start" and the "Completed"-event records for the same transaction on the same projection. Is this to be expected?

Best Answer

  • SruthiASruthiA Vertica Employee Administrator
    Answer ✓

    1) it is number of ros containers per projection
    2) in simple terms it is set or rows
    3) yes it is expected

Answers

  • Vertica will not be able to handle flood of small transactions, you will get problems from all sides.

  • @Sergey_Cherepan_1: Yes, we know that Vertica is not optimized for small transactions. However, we have a specific use case in our environment that could lead to such a scenario, and with the tests we want to find the thresholds where something goes wrong so we can define the boundaries there (and hopefully avoid/block them programmatically ).

  • @SruthiA Thnx for your answers.
    Rgd 2): Could you explain this perhaps a little bit more?
    Rgd 3): So does this mean that container_count shows the current number of ROS and not the number when the specific event was recorded?

  • SruthiASruthiA Vertica Employee Administrator
    edited February 3

    2) storage container a broad term. in vertica, there are 2 types : WOS and ROS. vertica is internally organized into a hybrid store consisting of two distinct storage structures. The Write-Optimized Store (WOS) container is a data structure that generally fits into main memory and is designed to efficiently support insert and update operations. Conversely, the Read-Optimized Store (ROS) container is a set of rows stored in a particular group of files and is both sorted and compressed, making it efficient to read and query one or more Projections. If you are interested to know more about vertica architecture, please go through the below white paper.

    https://docs.media.bitpipe.com/io_10x/io_102056/item_467954/The Vertica Analytic Platform Technical Overview White Paper.pdf

    3) it means that particular txn merged that many ros containers.

  • @SruthiA Thnx for the answers, but WOS was removed with Vertica 10.

  • SruthiASruthiA Vertica Employee Administrator

    @kfu : Yes. WOS was removed in vertica 10. I was trying to explain what is storage container.

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