diff options
Diffstat (limited to 'src/backend/storage/freespace/freespace.c')
| -rw-r--r-- | src/backend/storage/freespace/freespace.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/src/backend/storage/freespace/freespace.c b/src/backend/storage/freespace/freespace.c index d3f207b8540..849685f5a07 100644 --- a/src/backend/storage/freespace/freespace.c +++ b/src/backend/storage/freespace/freespace.c @@ -97,7 +97,16 @@ typedef struct /* Address of the root page. */ static const FSMAddress FSM_ROOT_ADDRESS = {FSM_ROOT_LEVEL, 0}; -/* Local map of block numbers for small heaps with no FSM. */ +/* + * For small relations, we don't create FSM to save space, instead we use + * local in-memory map of pages to try. To locate free space, we simply try + * pages directly without knowing ahead of time how much free space they have. + * + * Note that this map is used to the find the block with required free space + * for any given relation. We clear this map when we have found a block with + * enough free space, when we extend the relation, or on transaction abort. + * See src/backend/storage/freespace/README for further details. + */ typedef struct { BlockNumber nblocks; @@ -1175,5 +1184,13 @@ fsm_local_search(void) return target_block; } while (target_block > 0); + /* + * If we didn't find any available block to try in the local map, then + * clear it. This prevents us from using the map again without setting it + * first, which would otherwise lead to the same conclusion again and + * again. + */ + FSMClearLocalMap(); + return InvalidBlockNumber; } |