diff options
Diffstat (limited to 'src/include/storage/bufpage.h')
| -rw-r--r-- | src/include/storage/bufpage.h | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h index 85cd0abb972..87f16557ba5 100644 --- a/src/include/storage/bufpage.h +++ b/src/include/storage/bufpage.h @@ -53,14 +53,18 @@ * * NOTES: * - * linp1..N form an ItemId array. ItemPointers point into this array - * rather than pointing directly to a tuple. Note that OffsetNumbers + * linp1..N form an ItemId (line pointer) array. ItemPointers point + * to a physical block number and a logical offset (line pointer + * number) within that block/page. Note that OffsetNumbers * conventionally start at 1, not 0. * - * tuple1..N are added "backwards" on the page. because a tuple's - * ItemPointer points to its ItemId entry rather than its actual + * tuple1..N are added "backwards" on the page. Since an ItemPointer + * offset is used to access an ItemId entry rather than an actual * byte-offset position, tuples can be physically shuffled on a page - * whenever the need arises. + * whenever the need arises. This indirection also keeps crash recovery + * relatively simple, because the low-level details of page space + * management can be controlled by standard buffer page code during + * logging, and during recovery. * * AM-generic per-page information is kept in PageHeaderData. * @@ -233,7 +237,7 @@ typedef PageHeaderData *PageHeader; /* * PageGetContents - * To be used in case the page does not contain item pointers. + * To be used in cases where the page does not contain line pointers. * * Note: prior to 8.3 this was not guaranteed to yield a MAXALIGN'd result. * Now it is. Beware of old code that might think the offset to the contents |