Interpreting the Executed Visualization plan in SAP HANA

[former_member229412]

Hi All,

I have been trying to understand the Visualization plan of a Calculated view to tune it up for better performance. While going through graphical plan, I could find at some nodes, there are huge number of records (about 3 Billion) shown as Output Cardinality Estimated while the actual records returned are only few thousands(Refer picture below). I am confused why so many records are being looked up.

I am looking for answers to following

1. What is the significance of this Estimated cardinality? (Not sure if I have to worry about this as my query is being executed in a minute)

2. Are there any documents to understand how to rightly interpret the Visualization plan?

[former_member229412]

Does anybody have answer to this.

[former_member229412]

Any answers/comments pls

[lbreddemann]

There had been several threads and blog posts on plan viz in SAP HANA covering basics and specific questions alike.

By now there's even at least one book out covering plan viz exclusively.

So, all in all, I'd say there's a fair share of information you can work through that will answer your questions.

Considering that you ask about the significance of estimated vs. actual cardinality, I'd recommend getting a grip on general query optimisation where such foundations are laid out.

[former_member229412]

Thanks for the comment Lars. I have tried searching for threads before posting the question, but I couldn't get any relevant one. Probably I still need to get used to revamped portal. I would try searching again.

And yes I found one book in SAP Press covering Plan viz exclusively. will check that too.

[former_member229412]

Somehow I am not getting any relevant threads while searching this portal. SDN/SCN (old portal) were so much better and intuitive.

Now I go to Community section and Q&A sub section, and search for SAP HANA Plan Viz, i get few threads and none seem relevant.

It looks as if there is no body in the community and I am in a empty room.

[lbreddemann]

You're definitively not the only one feeling that way.

It is s unfortunately visible everywhere here in the new SAP community. Discussions around this are ongoing (mostly in the "coffee corner" https://answers.sap.com/content/kbentry/list.html ) and a lot of people are working on "making SCN great again...".

A lot of the previous content is google-findable and has by now been migrated. So, that's what I use...

[former_member815780]

Hi, prashanth.avula!

I know it's been a long time but I also struggled to find this information, so I'll post here just in case someone else needs it.

Refer to official SAP help portal documentation for a complete explanation of this topic: Actual versus Estimated Size

Best regards,

Felipe

[FCI]

Interesting. Thx.

I guess next step will be to understand what you can do in case of wrong size estimation...