importccl: support unchecked foreign keys in IMPORT PGDUMP

[maddyblue]

We achieve this by implementing sql.SchemaResolver with a map from the
found tables in the IMPORT and using that to resolve table names during
FK creation.

Release note (sql change): support foreign keys in IMPORT PGDUMP.

[cockroach-teamcity]

This change is 

[dt]

Reviewed 6 of 6 files at r1.
Reviewable status: complete! 0 of 0 LGTMs obtained

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pkg/ccl/importccl/import_stmt.go, line 259 at r1 (raw file):

// Implements the sql.SchemaResolver interface.
func (r fkResolver) LogicalSchemaAccessor() sql.SchemaAccessor {
	return nil

I'm a little wary of returning zero values rather than panicking if we think we'll never be called, just in case we start silently returning non-sense later and it goes undetected. /¢2.

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pkg/ccl/importccl/read_import_pgdump.go, line 254 at r1 (raw file):

				switch cmd := cmd.(type) {
				case *tree.AlterTableAddConstraint:
					create.Defs = append(create.Defs, cmd.ConstraintDef)

this is going to break on circular reference relationships.

I think we'll need to evaluate all the CREATEs into descs, then modify the descs to add the FKs rather than letting MakeSimpleTableDesc do it for us.

More than happy to punt that to a follow up though.

[maddyblue]

Reviewable status: complete! 0 of 0 LGTMs obtained

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pkg/ccl/importccl/import_stmt.go, line 259 at r1 (raw file):

Previously, dt (David Taylor) wrote…

I'm a little wary of returning zero values rather than panicking if we think we'll never be called, just in case we start silently returning non-sense later and it goes undetected. /¢2.

I agree. And it's unclear what to do here. I feel like explicitly panicking here is wrong, but returning a nil will just panic somewhere else for maybe an unclear reason? Dunno. I'm going to merge as is and we can change it if we need to.

[maddyblue]

bors r+

[craig]

Build failed

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[maddyblue]

bors r+

[craig]

Build failed

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[maddyblue]

bors r+

[craig]

Build succeeded

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