docs/tech-notes: update "Statement Execution" and "Building execution plans" sections of "Life of a query"

[mneverov]

docs/tech-notes: update "Statement Execution" and "Building execution plans" sections of "Life of a query"

Release note: None

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This change is 

[RaduBerinde]

Thanks for the updates!

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @mneverov)

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docs/tech-notes/life_of_a_query.md, line 189 at r1 (raw file):

children whose data it consumes).
                                
SQL query planning and optimizations are described in details in the 

[nit] in detail

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docs/tech-notes/life_of_a_query.md, line 192 at r1 (raw file):

documentation for the [`opt` package](https://github.com/cockroachdb/cockroach/blob/9969862335cf501c1aa67a4aaf018ad5dc8e85e8/pkg/sql/opt/doc.go). 

In the meantime, the plan `Builder` [looks at the type of the

remove "in the meantime"
say the optbuilder instead of Builder (we have an execbuilder.Builder too)

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docs/tech-notes/life_of_a_query.md, line 202 at r1 (raw file):

[`builder.buildScan()`](https://github.com/cockroachdb/cockroach/blob/9969862335cf501c1aa67a4aaf018ad5dc8e85e8/pkg/sql/opt/optbuilder/select.go#L114))
to scan a table, a `WHERE` clause is transformed into an [`memo.FilterExpr`](https://github.com/cockroachdb/cockroach/blob/9969862335cf501c1aa67a4aaf018ad5dc8e85e8/pkg/sql/opt/optbuilder/select.go#L1126),
an `ORDER BY` clause is [ordering physical property](https://github.com/cockroachdb/cockroach/blob/9969862335cf501c1aa67a4aaf018ad5dc8e85e8/pkg/sql/opt/optbuilder/orderby.go#L65),

[nit] is turned into

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docs/tech-notes/life_of_a_query.md, line 208 at r1 (raw file):

Finally, the execution plan is simplified, [optimized](https://github.com/cockroachdb/cockroach/blob/5ee1f52f0eef1eeceddde16aad5002dc31ca08cb/pkg/sql/opt/xform/optimizer.go#L198), and
a physical plan is built.

I'd add a bit more detail about how the physical plan is built: the execbuilder generates execution operators through an exec.Factory (implemented by sql/opt_factory.go)

[blathers-crl]

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[mneverov]

Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale) (waiting on @RaduBerinde)

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docs/tech-notes/life_of_a_query.md, line 189 at r1 (raw file):

Previously, RaduBerinde wrote…

[nit] in detail

done

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docs/tech-notes/life_of_a_query.md, line 192 at r1 (raw file):

Previously, RaduBerinde wrote…

remove "in the meantime"
say the optbuilder instead of Builder (we have an execbuilder.Builder too)

done

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docs/tech-notes/life_of_a_query.md, line 202 at r1 (raw file):

Previously, RaduBerinde wrote…

[nit] is turned into

done

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docs/tech-notes/life_of_a_query.md, line 208 at r1 (raw file):

Previously, RaduBerinde wrote…

I'd add a bit more detail about how the physical plan is built: the execbuilder generates execution operators through an exec.Factory (implemented by sql/opt_factory.go)

Added some info about physical plan building.

[RaduBerinde]

Reviewable status: complete! 1 of 0 LGTMs obtained

[yuzefovich]

Thanks a lot for the update! I have a couple of nits.

Reviewed 1 of 1 files at r2.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @mneverov)

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docs/tech-notes/life_of_a_query.md, line 157 at r2 (raw file):

documentation](https://www.cockroachlabs.com/docs/stable/transactions.html#client-side-intervention).
The statement execution code path continues inside the 
[`callback`](https://github.com/cockroachdb/cockroach/blob/9969862335cf501c1aa67a4aaf018ad5dc8e85e8/pkg/sql/conn_executor_prepare.go#L201), 

nit: I'm confused about this sentence and the link only adds to my confusion. I think I'd remove the sentence entirely.

Probably, originally "callback" referred to

cockroach/pkg/sql/executor.go

Line 604 in 33c18ad

txnClosure := func(txn *client.Txn, opt *client.TxnExecOptions) error {

, and I'm not sure what the equivalent to it now is, possibly it became obsolete / was refactored.

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docs/tech-notes/life_of_a_query.md, line 188 at r2 (raw file):

right`](https://github.com/cockroachdb/cockroach/blob/33c18ad1bcdb37ed6ed428b7527148977a8c566a/pkg/sql/join.go#L125)
children whose data it consumes).
                                

super nit: something is off here (as viewing from Reviewable), seems like unnecessary space characters?

[mneverov]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @yuzefovich)

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docs/tech-notes/life_of_a_query.md, line 157 at r2 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

nit: I'm confused about this sentence and the link only adds to my confusion. I think I'd remove the sentence entirely.

Probably, originally "callback" referred to

cockroach/pkg/sql/executor.go

Line 604 in 33c18ad

txnClosure := func(txn *client.Txn, opt *client.TxnExecOptions) error {

, and I'm not sure what the equivalent to it now is, possibly it became obsolete / was refactored.

yes, you're right. The previous statement related to runTxnAttempt(...) in the callback that did run the statement. The closure I mentioned just creates a memo for a prepared statement, but actual execution is don in dispatchToExecutionEngine().
Updated the PR.

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docs/tech-notes/life_of_a_query.md, line 188 at r2 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

super nit: something is off here (as viewing from Reviewable), seems like unnecessary space characters?

fixed, thx

[yuzefovich]

Awesome, thanks!

bors r=raduberinde,yuzefovich

Reviewed 1 of 1 files at r3.
Reviewable status: complete! 1 of 0 LGTMs obtained (and 1 stale) (waiting on @mneverov)

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docs/tech-notes/life_of_a_query.md, line 157 at r2 (raw file):

Previously, mneverov (Max Neverov) wrote…

yes, you're right. The previous statement related to runTxnAttempt(...) in the callback that did run the statement. The closure I mentioned just creates a memo for a prepared statement, but actual execution is don in dispatchToExecutionEngine().
Updated the PR.

Thanks!

[craig]

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[craig]

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