workload/schemachange: allow self deps in tableHasDependencies for DROP TABLE

This change updates tableHasDependencies to optionally include
self-referencing dependencies when skipSelfRef is false. This is
needed for DROP TABLE, where self-dependencies (e.g., from triggers)
are safe to ignore because they are cleaned up as part of the drop.

In contrast, RENAME TABLE must still block on these, since the
dependent reference would not be updated by the rename.

The function now takes a skipSelfRef flag to distinguish these cases,
and excludes only self-dependencies when skipSelfRef is true.

Informs #147514

Epic: None
Release note: none

Author: spilchen

pkg/workload/schemachange/error_screening.go

@@ -98,8 +98,16 @@ func (og *operationGenerator) fnExists(
 	)`, fnName, argTypes)
 }
 
+// tableHasDependencies reports whether the given table has any schema dependencies,
+// optionally excluding foreign keys and/or self-references.
+//
+// A dependency is ignored if:
+// 1. It is a foreign key and includeFKs is false.
+// 2. It is a self-dependency (i.e., the table depends on itself) and:
+// a) It is a foreign key, or
+// b) skipSelfRef is true (regardless of dependency type).
 func (og *operationGenerator) tableHasDependencies(
-	ctx context.Context, tx pgx.Tx, tableName *tree.TableName, includeFKs bool,
+	ctx context.Context, tx pgx.Tx, tableName *tree.TableName, includeFKs, skipSelfRef bool,
 ) (bool, error) {
 	fkFilter := ""
 	if !includeFKs {
@@ -117,12 +125,18 @@ func (og *operationGenerator) tableHasDependencies(
                             ns.oid = c.relnamespace
                      WHERE c.relname = $1 AND ns.nspname = $2
                 )
-           AND NOT (fd.descriptor_id = fd.dependedonby_id AND fd.dependedonby_type = 'fk')
+           AND NOT (
+             fd.descriptor_id = fd.dependedonby_id
+             AND (
+               fd.dependedonby_type = 'fk'
+               OR $3::BOOL = true
+             )
+           )
            AND fd.dependedonby_type != 'sequence'
            %s
        )
 	`, fkFilter)
-	return og.scanBool(ctx, tx, q, tableName.Object(), tableName.Schema())
+	return og.scanBool(ctx, tx, q, tableName.Object(), tableName.Schema(), skipSelfRef)
 }
 
 // columnRemovalWillDropFKBackingIndexes determines if dropping this column

pkg/workload/schemachange/operation_generator.go

@@ -2049,7 +2049,8 @@ func (og *operationGenerator) dropTable(ctx context.Context, tx pgx.Tx) (*opStmt
 	if err != nil {
 		return nil, err
 	}
-	tableHasDependencies, err := og.tableHasDependencies(ctx, tx, tableName, true /* includeFKs */)
+	tableHasDependencies, err := og.tableHasDependencies(ctx, tx, tableName, true, /* includeFKs */
+		true /* skipSelfRef */)
 	if err != nil {
 		return nil, err
 	}
@@ -2081,7 +2082,8 @@ func (og *operationGenerator) dropView(ctx context.Context, tx pgx.Tx) (*opStmt,
 	if err != nil {
 		return nil, err
 	}
-	viewHasDependencies, err := og.tableHasDependencies(ctx, tx, viewName, true /* includeFKs */)
+	viewHasDependencies, err := og.tableHasDependencies(ctx, tx, viewName, true, /* includeFKs */
+		true /* skipSelfRef */)
 	if err != nil {
 		return nil, err
 	}
@@ -2348,7 +2350,8 @@ func (og *operationGenerator) renameTable(ctx context.Context, tx pgx.Tx) (*opSt
 		return nil, err
 	}
 
-	srcTableHasDependencies, err := og.tableHasDependencies(ctx, tx, srcTableName, false /* includeFKs */)
+	srcTableHasDependencies, err := og.tableHasDependencies(ctx, tx, srcTableName, false, /* includeFKs */
+		false /* skipSelfRef */)
 	if err != nil {
 		return nil, err
 	}
@@ -2398,7 +2401,8 @@ func (og *operationGenerator) renameView(ctx context.Context, tx pgx.Tx) (*opStm
 		return nil, err
 	}
 
-	srcTableHasDependencies, err := og.tableHasDependencies(ctx, tx, srcViewName, true /* includeFKs */)
+	srcTableHasDependencies, err := og.tableHasDependencies(ctx, tx, srcViewName, true, /* includeFKs */
+		false /* skipSelfRef */)
 	if err != nil {
 		return nil, err
 	}