If you're interested in DB internals, stop what you're doing and watch @CMUDB Quarantine Talk from Nico+Cesar about @SQLServer's Cascades query optimizer: https://t.co/FCdsbHHEaD

Many talks this semester were good. This one is the best. My thread provides key takeaways

[6:50] Microsoft hired Goetz Graffe in the 1990s to help them rewrite original Sybase optimizer into Cascades. This framework is now used across all MSFT DB products (@SQLServer, @cosmosdb, @Azure_Synapse).
[14:43] The optimizer checks whether it has stats it will need before cost-based search. If not, it blocks planning until the DBMS generates them. This is different than other approaches we saw this semester where DBMS says "we'll do it live!" with whatever stats are available.
[21:05] Their Cascades' search starts small/simple and then they make decision on the fly whether to expand search based on the expected query runtime and performance benefit from more search.
[26:33] They explicitly have a property for Halloween Problem. Operators specify whether they protect from it and then optimizer ensures property is satisfied. This is mindblowing. I have never thought about using the optimizer for this but it makes sense. https://t.co/hjjoGCwyvl
[33:16] This is the menu of all the stats that they maintain for tables. Again, the latest research shows @SQLServer has the most accurate stats: https://t.co/d1btkxmsYf
[39:05] @SQLServer uses a general-purpose cardinality estimation framework. This allows them to programmatically select the best data structure to use per expression type. They rank choices by "quality of estimation". This needs further research.
[44:16] Question from @Lin_Ma_: Are you using ML for cardinality estimation?
Answer: @cosmosdb is using it. @SQLServer is more conservative and using a minor form of it.
[53:14] They use heuristics to pre-seed Cascades' memoization table with plans that they think will be good. This allows the search to start from a local optimum instead of a random location in search space.
[54:48] Optimizer uses logical timeouts (# of plans considered) instead of physical timeout (wallclock). This ensures that DBMS always produces plans with same quality under high load. Hand-tuned timeouts for different optimization stages.
[1:00:45] They also use pre-seeding to support DBA provided query plan hints! This is another genius idea that seems obvious once somebody shows it to you.
[1:03:32] This example shows the limitations of Cascades' tree-based plan search. For some optimizations, the DBMS must also consider hypergraphs. See Neumann SIGMOD'08: https://t.co/s825mXPMqK

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Or, you could let us know when you figure out why it was trending yesterday and the users are complaining which is why Vice wrote about it. Why I'm saying what I am.

There's an assumption here that this problem is fixed bc it was already hacked.

It's not.


We have ppl freezing and dying in TX right now because some ppl who thought they were really smart never spoke to anyone with actual experience with energy systems in extreme cold climates.

Texans are waiting for a solution to a preventable problem.

Farmers are saying that now, not during a crisis, they have to wait for a JD tech to arrive to help them.

The assumption that bc SOME farmers said screw this and used hacked firmware to get around that obstacle doesn't mean that all farmers are doing that.

If all farmers were using hacked firmware we wouldn't be discussing this right now would we?

Of course no one has pointed out that another issue here is that no one at John Deere has figured out they don't have enough staff to quickly and reliably SOLVE problems.

The locked firmware is just one of many issues here.

By not giving people a fast solution they're causing this and other issues.

So what I'm saying is somebody at John Deere needs to examine all of this.

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॥ॐ॥
अस्य श्री गायत्री ध्यान श्लोक:
(gAyatri dhyAna shlOka)
• This shloka to meditate personified form of वेदमाता गायत्री was given by Bhagwaan Brahma to Sage yAgnavalkya (याज्ञवल्क्य).

• 14th shloka of गायत्री कवचम् which is taken from वशिष्ठ संहिता, goes as follows..


• मुक्ता-विद्रुम-हेम-नील धवलच्छायैर्मुखस्त्रीक्षणै:।
muktA vidruma hEma nIla dhavalachhAyaiH mukhaistrlkShaNaiH.

• युक्तामिन्दुकला-निबद्धमुकुटां तत्वार्थवर्णात्मिकाम्॥
yuktAmindukalA nibaddha makutAm tatvArtha varNAtmikam.

• गायत्रीं वरदाभयाङ्कुश कशां शुभ्रं कपालं गदाम्।
gAyatrIm vardAbhayANkusha kashAm shubhram kapAlam gadAm.

• शंखं चक्रमथारविन्दयुगलं हस्तैर्वहन्ती भजै॥
shankham chakramathArvinda yugalam hastairvahantIm bhajE.

This shloka describes the form of वेदमाता गायत्री.

• It says, "She has five faces which shine with the colours of a Pearl 'मुक्ता', Coral 'विद्रुम', Gold 'हेम्', Sapphire 'नील्', & a Diamond 'धवलम्'.

• These five faces are symbolic of the five primordial elements called पञ्चमहाभूत:' which makes up the entire existence.

• These are the elements of SPACE, FIRE, WIND, EARTH & WATER.

• All these five faces shine with three eyes 'त्रिक्षणै:'.