covering index of btree interior pages

[mlin]

No description provided.

[mlin]

The current computation for btree_interior is a heuristic that admits false-positives. (Overflow, ptrmap, and freelist pages may have 2 or 5 in the first byte.) This leads to unnecessary data duplication, perhaps worsening as the database grows (as a proportion of the database size)

Additional heuristics can ameliorate this, perhaps sufficiently:

• right-most pointer must be less than database page count
• number of fragmented free bytes must be below 60
• offset of first freeblock must follow start of the cell content area
• number of cells cannot exceed page size / 5 - 1
• cell pointers must all be >= start of the cell content area, and all pairs must have a difference of at least 5
• cell left pointers must be less than database page count