diff options
Diffstat (limited to 'src/include/storage/relfilenode.h')
| -rw-r--r-- | src/include/storage/relfilenode.h | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/src/include/storage/relfilenode.h b/src/include/storage/relfilenode.h index 60c38295375..5ec1d8f7177 100644 --- a/src/include/storage/relfilenode.h +++ b/src/include/storage/relfilenode.h @@ -69,6 +69,10 @@ typedef enum ForkNumber * Note: in pg_class, relfilenode can be zero to denote that the relation * is a "mapped" relation, whose current true filenode number is available * from relmapper.c. Again, this case is NOT allowed in RelFileNodes. + * + * Note: various places use RelFileNode in hashtable keys. Therefore, + * there *must not* be any unused padding bytes in this struct. That + * should be safe as long as all the fields are of type Oid. */ typedef struct RelFileNode { @@ -79,7 +83,11 @@ typedef struct RelFileNode /* * Augmenting a relfilenode with the backend ID provides all the information - * we need to locate the physical storage. + * we need to locate the physical storage. The backend ID is InvalidBackendId + * for regular relations (those accessible to more than one backend), or the + * owning backend's ID for backend-local relations. Backend-local relations + * are always transient and removed in case of a database crash; they are + * never WAL-logged or fsync'd. */ typedef struct RelFileNodeBackend { @@ -87,11 +95,15 @@ typedef struct RelFileNodeBackend BackendId backend; } RelFileNodeBackend; +#define RelFileNodeBackendIsTemp(rnode) \ + ((rnode).backend != InvalidBackendId) + /* * Note: RelFileNodeEquals and RelFileNodeBackendEquals compare relNode first * since that is most likely to be different in two unequal RelFileNodes. It * is probably redundant to compare spcNode if the other fields are found equal, - * but do it anyway to be sure. + * but do it anyway to be sure. Likewise for checking the backend ID in + * RelFileNodeBackendEquals. */ #define RelFileNodeEquals(node1, node2) \ ((node1).relNode == (node2).relNode && \ |