On Sun, Apr 7, 2024 at 9:08 AM John Naylor <johncnaylo...@gmail.com> wrote:
>
> I've attached a mostly-polished update on runtime embeddable values,
> storing up to 3 offsets in the child pointer (1 on 32-bit platforms).
> As discussed, this includes a macro to cap max possible offset that
> can be stored in the bitmap, which I believe only reduces the valid
> offset range for 32kB pages on 32-bit platforms. Even there, it allows
> for more line pointers than can possibly be useful. It also splits
> into two parts for readability. It would be committed in two pieces as
> well, since they are independently useful.
I pushed both of these and see that mylodon complains that anonymous
unions are a C11 feature. I'm not actually sure that the union with
uintptr_t is actually needed, though, since that's not accessed as
such here. The simplest thing seems to get rid if the union and name
the inner struct "header", as in the attached.
diff --git a/src/backend/access/common/tidstore.c b/src/backend/access/common/tidstore.c
index cddbaf013b..78730797d6 100644
--- a/src/backend/access/common/tidstore.c
+++ b/src/backend/access/common/tidstore.c
@@ -43,35 +43,30 @@
*/
typedef struct BlocktableEntry
{
- union
+ struct
{
- struct
- {
#ifndef WORDS_BIGENDIAN
- /*
- * We need to position this member so that the backing radix tree
- * can use the lowest bit for a pointer tag. In particular, it
- * must be placed within 'header' so that it corresponds to the
- * lowest byte in 'ptr'. We position 'nwords' along with it to
- * avoid struct padding.
- */
- uint8 flags;
-
- int8 nwords;
+ /*
+ * We need to position this member so that the backing radix tree can
+ * use the lowest bit for a pointer tag. In particular, it must be
+ * placed within 'header' so that it corresponds to the lowest byte in
+ * 'ptr'. We position 'nwords' along with it to avoid struct padding.
+ */
+ uint8 flags;
+
+ int8 nwords;
#endif
- /*
- * We can store a small number of offsets here to avoid wasting
- * space with a sparse bitmap.
- */
- OffsetNumber full_offsets[NUM_FULL_OFFSETS];
+ /*
+ * We can store a small number of offsets here to avoid wasting space
+ * with a sparse bitmap.
+ */
+ OffsetNumber full_offsets[NUM_FULL_OFFSETS];
#ifdef WORDS_BIGENDIAN
- int8 nwords;
- uint8 flags;
+ int8 nwords;
+ uint8 flags;
#endif
- };
- uintptr_t ptr;
} header;
bitmapword words[FLEXIBLE_ARRAY_MEMBER];
