sql: add a virtual index on the pg_catalog.pg_type.OID

[ekalinin]

Fixes #49208

Release note (performance improvement): scans over virtual
table pg_type by OID column have improved performance in common cases.

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[blathers-crl]

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[rohany]

Hey @ekalinin, thanks for your contribution! However, this doesn't do what we want. Right now, your virtual index is ignoring the input constraint value and generating all rows of the table instead. You should be using the input constraint to return only the row of the oid requested.

[ekalinin]

Hey @ekalinin, thanks for your contribution! However, this doesn't do what we want. Right now, your virtual index is ignoring the input constraint value and generating all rows of the table instead. You should be using the input constraint to return only the row of the oid requested.

Thanks for response, @rohany !
Could you help me with this?

I'm trying to use the input constraint value like this:

	indexes: []virtualIndex{
		{
			partial: false,
			populate: func(ctx context.Context, constraint tree.Datum, p *planner, db *sqlbase.ImmutableDatabaseDescriptor,
				addRow func(...tree.Datum) error) (bool, error) {
				oid := tree.MustBeDOid(constraint)
				fmt.Printf("--> populate index: oid: %+v\n", oid)
				tbl, err := p.LookupTableByID(ctx, sqlbase.ID(oid.DInt))
				if err != nil {
					fmt.Printf("--> populate index: lookup err=%+v\n", err)
					if sqlbase.IsUndefinedRelationError(err) {
						fmt.Printf("--> populate index: IsUndefinedRelationError\n")
						return false, nil
					}
					return false, err
				}
  // ...

and getting an error:

➜ ./cockroach demo 
root@127.0.0.1:34233/movr> select * from pg_type where oid = 1000;
--> populate index: oid: 1000
--> populate index: lookup err=relation "[1000]" does not exist

[rohany]

You're on the right track! You'll first want to check if the input oid is one of the predefined type oids. If not, then you'll want to look up the oid's TypeDescriptor. Note that the oid of a type doesn't directly correspond to its descriptor ID. You have to use types.UserDefinedTypeOIDToID to do the conversion.

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[ekalinin]

You're on the right track! You'll first want to check if the input oid is one of the predefined type oids. If not, then you'll want to look up the oid's TypeDescriptor. Note that the oid of a type doesn't directly correspond to its descriptor ID. You have to use types.UserDefinedTypeOIDToID to do the conversion.

Hey @rohany! Thanks for the hints! I hope i understood them correctly.
PTAL.

[rohany]

Looking good! Just 2 more small requests.

[rohany]

Thanks for the contribution! This is ready to go.

bors r=rohany

[craig]

Build succeeded

• GitHub CI (Cockroach)