suggest

const (
	// CaveatNonTransactional: the recommended sequence contains a
	// CONCURRENTLY statement, which cannot run inside a transaction
	// block.
	CaveatNonTransactional Caveat = "non-transactional"
	// CaveatSeparateTransactions: the steps must commit separately — the
	// weaker locks the sequence exists for are held to commit, so one
	// enclosing transaction reproduces the blocking the rewrite avoids.
	CaveatSeparateTransactions Caveat = "separate-transactions"
	// CaveatInvalidIndexOnFailure: a failed or cancelled concurrent build
	// leaves an INVALID index that must be detected (pg_index.indisvalid)
	// and dropped or rebuilt; the engine's executor owns that check when
	// it runs the sequence.
	CaveatInvalidIndexOnFailure Caveat = "invalid-index-on-failure"
	// CaveatDetachFinalizeOnFailure: an interrupted concurrent detach
	// leaves the partition half-detached; it must be finished with
	// DETACH PARTITION FINALIZE.
	CaveatDetachFinalizeOnFailure Caveat = "detach-finalize-on-failure"
	// CaveatValidationScan: the VALIDATE step still scans every row — the
	// rewrite trades the lock strength, not the scan.
	CaveatValidationScan Caveat = "validation-scan"
	// CaveatScaffoldConstraintOnFailure: a failed VALIDATE leaves the
	// NOT VALID constraint the sequence added on the live table, and
	// replaying the sequence then fails at the ADD CONSTRAINT step
	// (duplicate_object) — the runner must detect the leftover constraint
	// (pg_constraint) and resume from the VALIDATE step, or drop it and
	// restart.
	CaveatScaffoldConstraintOnFailure Caveat = "scaffold-constraint-on-failure"
)

const (
	// GuidanceSplitStatement: rewrites are constructed only for
	// single-operation statements — a partial rewrite of a compound ALTER
	// would be misleading. Split the statement into one operation per
	// statement and advise again.
	GuidanceSplitStatement Guidance = "split-statement"
	// GuidanceAddColumnThenConstraint: an inline UNIQUE / PRIMARY KEY /
	// FOREIGN KEY / CHECK on ADD COLUMN builds or validates under the ADD
	// COLUMN's ACCESS EXCLUSIVE lock. Add the plain column first, then
	// build the constraint with its online pattern as a separate, named
	// ADD CONSTRAINT — named, because the unnamed ADD CHECK / ADD FOREIGN
	// KEY forms are themselves refused (GuidanceNameConstraintThenValidate).
	GuidanceAddColumnThenConstraint Guidance = "add-column-then-constraint"
	// GuidancePrevalidatedCheck: ATTACH PARTITION scans the child under
	// the parent's lock unless a validated CHECK matching the partition
	// bound already exists on the child. Pre-add that CHECK (NOT VALID,
	// then VALIDATE), attach, then drop it. The planner cannot construct
	// the bound-matching CHECK from the statement alone.
	GuidancePrevalidatedCheck Guidance = "pre-add-validated-check"
	// GuidanceNotNullScaffold: prove the invariant with a NOT VALID CHECK
	// (col IS NOT NULL) plus an online VALIDATE, then the NOT NULL
	// constraint is a catalog flip — the same scaffold sequence the
	// SET NOT NULL form gets constructed.
	GuidanceNotNullScaffold Guidance = "not-null-scaffold"
	// GuidanceNameConstraintThenValidate: an unnamed ADD CHECK / ADD
	// FOREIGN KEY has no constructible rewrite because the online
	// sequence's VALIDATE CONSTRAINT step needs the constraint's name and
	// the server assigns one only at creation. Name the constraint, add
	// it NOT VALID, then VALIDATE it online.
	GuidanceNameConstraintThenValidate Guidance = "name-constraint-then-validate"
	// GuidanceUniqueIndexThenConstraint: an ADD PRIMARY KEY / ADD UNIQUE
	// whose USING INDEX rewrite could not be constructed. Build the unique
	// index with CREATE UNIQUE INDEX CONCURRENTLY, then attach it with
	// ADD CONSTRAINT … USING INDEX — the same sequence the constructed
	// rewrite emits. Keeps ManualGuidance total over every constraint kind
	// the classifier can mark safer-idiom, so a parser shape that yields
	// no rewrite becomes advice rather than a failed report.
	GuidanceUniqueIndexThenConstraint Guidance = "unique-index-then-constraint"
)