schemachanger: address index validation errors during pk swap

[fqazi]

Previously, when mutations were made public for validation queries, the declarative schema changer primary key swaps were not appropriately handled. This could lead to scenarios where queries would be unable to find columns in recreated secondary indexes that should ideally exist (i.e. columns from the old primary key). This would cause validation to fail on these newly created indexes. To address, this patch adds logic for making declarative primary key swaps mutations properly by detecting them.

Fixes: #118626

Release note (bug fix): ALTER PRIMARY KEY could fail with a "non-nullable column with no value! Index scanned .." when validating recreated secondary indexes.

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[cockroach-teamcity]

This change is 

[rafiss]

nice fix! just had some nits about comments

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

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pkg/sql/catalog/descriptor.go line 764 at r1 (raw file):

	// IsPrimaryKeySwapMutation returns true if the mutation is a primary key
	// swap mutation or a secondary index used by the declarative schema changer
	// for an index swap.

nit: "for an index swap" -> "for a primary index swap"

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pkg/sql/catalog/tabledesc/table_desc.go line 650 at r1 (raw file):

		// and does not use a PrimaryKeySwap mutation for this operation. Instead,
		// it will create a new secondary index with a primary index encoding and
		// make it public later. To detect a primary index swap scenario we are going

i didn't follow this sentence:

"To detect a primary index swap scenario we are going for the declarative case detect the encoding type and if the index is going public."

missing words?

[fqazi]

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

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pkg/sql/catalog/tabledesc/table_desc.go line 650 at r1 (raw file):

Previously, rafiss (Rafi Shamim) wrote…

i didn't follow this sentence:

"To detect a primary index swap scenario we are going for the declarative case detect the encoding type and if the index is going public."

missing words?

Yeah this was badly worded, clarified the language here:

// The declarative schema changer handles primary key swaps differently and
// does not use a PrimaryKeySwap mutation for this operation. Instead, it
// will create a new secondary index with a primary index encoding as an index
// mutation. In the declarative schema changer case, to detect a primary index
// swap scenario, we are going to detect the encoding type of the index and
// check if a declarative scpb.PrimaryIndex element with a matching ID exists
// with a public target state. Since a table can only have a single primary
// index at a time, this would indicate this primary index is replacing the
// existing primary index.

[fqazi]

@rafiss TFTR!

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

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