Re: Partition Pruning

[Mattias Jonsson]

To see how it works, you can look for MONOTONIC in the source.

from item.h:
typedef enum monotonicity_info
{
NON_MONOTONIC, /* none of the below holds */
MONOTONIC_INCREASING, /* F() is unary and (x < y) => (F(x) <= F(y)) */
MONOTONIC_INCREASING_NOT_NULL, /* But only for valid/real x and y */
MONOTONIC_STRICT_INCREASING,/* F() is unary and (x < y) => (F(x) < F(y)) */
MONOTONIC_STRICT_INCREASING_NOT_NULL /* But only for valid/real x and y */
} enum_monotonicity_info;

It has to search the first partition if the partitioning function is MONOTONIC_*_INCREASING_NOT_NULL (only TO_DAYS is). So if the partitioning function is '(int_col)' it will never look for a NULL for a range query.

If you use the COLUMNS partitioning in 5.5 you can use a DATE/DATETIME column directly and it will not need the TO_DAYS() function and will not have this problem.