Index rows containing variable-length columns require more overhead than index rows containing only fixed-length values.
Use this formula if the index contains only fixed-length keys and are defined as NOT NULL:
Formula |
||
|---|---|---|
7 |
(Overhead) |
|
+ |
Sum of fixed-length keys |
|
= Size of leaf index row |
||
Use this formula if the index contains any variable-length keys or columns defined as NULL:
Formula |
Example |
|||
|---|---|---|---|---|
9 |
(Overhead) |
9 |
||
+ |
Sum of length of fixed-length keys |
+ |
4 |
|
+ |
Sum of length of variable-length keys |
+ |
20 |
|
+ |
Number of variable-length keys + 1 |
+ |
2 |
|
= Subtotal |
35 |
|||
|
||||
+ |
(Subtotal / 256) + 1 (overhead) |
+ |
1 |
|
= Size of leaf index row |
36 |
|||
