sql: refactor setval() to be a schema change for cached sequences

Sequences with cached values invalidate values when new descriptor
versions are seen. Previously, setval() was not a schema change, so
it did not invalidate the cache when called. This change ensures that
setval() is a schema change for cached sequences so that cached
values get invalidated when setval() is called.

Release note: None

pkg/sql/logictest/testdata/logic_test/sequences

@@ -1327,5 +1327,23 @@ SELECT last_value FROM cache_test
 ----
 70
 
+# Verify that setval() will invalidate the cache.
+
+query I
+SELECT setval('cache_test', 81, false)
+----
+81
+
+# 10 new values (81,82,...,90) are cached.
+query I
+SELECT nextval('cache_test')
+----
+81
+
+query I
+SELECT last_value FROM cache_test
+----
+90
+
 statement ok
 DROP SEQUENCE cache_test

pkg/sql/sequence.go

@@ -211,10 +211,26 @@ func (p *planner) SetSequenceValue(
 		return err
 	}
 
-	// TODO(vilterp): not supposed to mix usage of Inc and Put on a key,
-	// according to comments on Inc operation. Switch to Inc if `desired-current`
-	// overflows correctly.
-	return p.txn.Put(ctx, seqValueKey, newVal)
+	if descriptor.GetSequenceOpts().CacheSize <= 1 {
+		// TODO(vilterp): not supposed to mix usage of Inc and Put on a key,
+		// according to comments on Inc operation. Switch to Inc if `desired-current`
+		// overflows correctly.
+		return p.txn.Put(ctx, seqValueKey, newVal)
+	}
+
+	// If there are cached values, changing the value of the sequence should invalidate the cache.
+	// For simplicity, the cache invalidates implicitly when it sees new descriptor versions. Thus,
+	// a schema change is triggered here to make sure the cache gets invalidated.
+	mutableDescriptor, err := resolver.ResolveMutableExistingTableObject(ctx, p, seqName, true, tree.ResolveRequireSequenceDesc)
+
+	if err := p.txn.Put(ctx, seqValueKey, newVal); err != nil {
+		return err
+	}
+
+	if err != nil {
+		return err
+	}
+	return p.writeSchemaChange(ctx, mutableDescriptor, descpb.InvalidMutationID, fmt.Sprintf("setval('%s')", seqName.String()))
 }
 
 // MakeSequenceKeyVal returns the key and value of a sequence being set