DMVs Waits Cookbook Scripts XEvents SPs Catalog Functions Errors T-SQL Arch Ops

Of a heap

Analytics Platform System (PDW)

SQL database in Microsoft

Fabric

You can use the following steps to estimate the amount of space that is required to store data

in a heap:

  1. Specify the number of rows that will be present in the table:

= number of rows in the table

  1. Specify the number of fixed-length and variable-length columns and calculate the space

that is required for their storage:

Calculate the space that each of these groups of columns occupies within the data row.

The size of a column depends on the data type and length specification.

= total number of columns (fixed-length and variable-length)

= total byte size of all fixed-length columns

= number of variable-length columns

= maximum total byte size of all variable-length columns

  1. Part of the row, known as the null bitmap, is reserved to manage column nullability.

Calculate its size:

= 2 + ((

    1. / 8)

Only the integer part of this expression should be used. Discard any remainder.

  1. Calculate the variable-length data size:

If there are variable-length columns in the table, determine how much space is used to

store the columns within the row:

= 2 + (

x 2) +

The bytes added to

are for tracking each variable-length column. This

formula assumes that all variable-length columns are 100 percent full. If you anticipate

that a smaller percentage of the variable-length column storage space will be used, you

can adjust the

value by that percentage to yield a more accurate estimate

of the overall table size.

７

Note