BytesPerTableRow Struct Reference

This struct represents the number of bytes we expect to read for a table row. More...

#include <cost_model.h>

Public Attributes
int64_t	record_bytes
	The number of bytes read from the B-tree record. More...
int64_t	overflow_bytes
	The number of bytes read from overflow pages. More...
double	overflow_probability

Detailed Description

This struct represents the number of bytes we expect to read for a table row.

Note that the split between b-tree and overflow pages is specific to InnoDB and may not be a good fit for other storage engines. Ideally we should calculate row size and IO-cost in the handler, in a way that is specific to each particular storage engine. When using the DYNAMIC row format, an InnoDB B-tree record cannot be bigger than about half a page. (The default page size is 16KB). Above that, the longest fields are stored in separate overflow pages.

Member Data Documentation

overflow_bytes

int64_t BytesPerTableRow::overflow_bytes

The number of bytes read from overflow pages.

This is the combined size of those long variable-sized fields that are in the projection but stored in overflow pages.

overflow_probability

double BytesPerTableRow::overflow_probability

record_bytes

int64_t BytesPerTableRow::record_bytes

The number of bytes read from the B-tree record.

This also includes those fields that were not in the projection.

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The documentation for this struct was generated from the following file:

• sql/join_optimizer/cost_model.h