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Calculate the row size per table in a database

Antonios Chatzipavlis

Σε συνέχεια από το άρθρο μου για τα Row Overflow Page έφτιαξα μια stored procedure που υπολογίζει το μέγεθος του row ανά table

Σε αυτή δεν έχω συμπεριλάβει τα πάντα στον υπολογισμό αλλά αυτό δεν είναι κάτι προβληματικό καθώς η κεντρική ιδέα είναι να μπορεί κανείς να έχει μια πληροφορία που αγγίζει τη πραγματικότητα και μια διαφορά της τάξεως των 2-5 bytes είναι αμελητέα

Απλά εκτελέστε το παρακάτω κώδικα ο οποίος δημιουργεί την sp_EstimatedTablesRowSize στην master database και την κάνει system object ώστε να είναι διαθέσιμη σε κάθε database και με use την database απλά εκτελέστε την.

Στα σχόλια της stored procedure υπάρχουν οι απαραίτητες πληροφορίες

use master

    EXEC ('CREATE PROC dbo.sp_EstimatedTablesRowSize AS SELECT ''stub version, to be replaced''')

alter proc sp_EstimatedTablesRowSize
    by Antonios Chatzipavlis - SQLschool.gr

    Version History            Remarks
    1.0        2016-10-06        Initial Version
                            - Calculates all tables as HEAP
                            - Does not take into account indexes
                            - Bit data type calculated as 1/8th of byte
                            - Shows and calculates the maximum row size per table (max size from all columns)
                            - The minimum size of row size is 9 bytes because heap record cannot be smaller than forwarding stub size
                            - Calclulations based on BOL page https://msdn.microsoft.com/en-us/library/ms189124.aspx
                            - Return values
                                schema_name        : Name of table schema
                                table_name        : Name of table
                                num_cols        : Number of all table columns
                                num_variable_cols    : Number of variable lenght columns
                                row_size_bytes        : Row size in bytes

    Feedback: mailto:help@sqlschool.gr
    sp_EstimatedTablesRowSize is free to download and use for personal, educational, and internal 
    corporate purposes, provided that this header is preserved. Redistribution or sale 
    of sp_EstimatedTablesRowSize, in whole or in part, is prohibited without the author's express 
    written consent.
    with v0 as
            s.name as schemas_name           
           ,    o.name as table_name
           ,    c.name as column_name
           ,    t.name as data_type
           ,    c.is_nullable as allows_null
           ,    cast ( case  
            when t.name='bit' then 1/8
            when t.name='image' then 2147483647
            when t.name='text' then 2147483647
            when t.name='ntext' then 1073741834
            when t.name='xml' then 2147483647
            when t.name='geometry' then 2147483647
            when t.name='geography' then 2147483647
            when t.name='varchar' and c.max_length=-1 then 2147483647
            when t.name='nvarchar' and c.max_length=-1 then 2147483647
            when t.name='varbinary' and c.max_length=-1 then 2147483647
            else c.max_length 
            end as bigint) as col_lenght_bytes
           ,    c.precision  as col_precision
           ,    t.max_length as type_lenght_bytes
           ,    t.precision  as type_precision
           ,    case 
            when t.name in ('varchar','nvarchar','varbinary'
                then 1
            else 0
            end as is_var_length
           from        sys.objects        as o 
           inner join   sys.schemas        as s on s.schema_id = o.schema_id
           inner join   sys.columns        as c on c.object_id = o.object_id
           inner join   sys.types        as t on t.user_type_id = c.user_type_id
           where o.type='U'
    ), v1 as
        select  distinct
        ,       table_name
        ,       count(column_name) over (partition by schemas_name,table_name ) as num_cols
        ,    sum(case when is_var_length = 0 then col_lenght_bytes else 0 end) over (partition by schemas_name,table_name) as fixed_data_size 
        ,    count(case when is_var_length = 1 then column_name else null end) over (partition by schemas_name,table_name) as num_variable_cols 
        ,       sum(case when is_var_length = 1 then col_lenght_bytes else 0 end) over (partition by schemas_name,table_name)  as max_var_size 
        from v0 
    ), v2 as
        select    schemas_name
        ,    table_name
        ,    num_cols
        ,    num_variable_cols
        ,    fixed_data_size 
            + case when num_variable_cols > 0 then (2+(num_variable_cols*2) + max_var_size) else 0 end  -- variable data size
            + (2 + ( ( v1.num_cols + 7 ) / 8 )) -- null bitmap
            + 4 -- header overhead
            as row_size
        from v1
    ), v3 as
        select    v2.schemas_name as [schema_name]
        ,    v2.table_name
        ,    v2.num_cols
        ,    v2.num_variable_cols
        ,    case
            when v2.row_size < 9 then 9 -- heap record cannot be smaller than forwarding stub size
            else v2.row_size
            end as row_size_bytes
        from v2 
    select * from v3
    order by 1,2;

-- make it system object
EXEC sys.sp_MS_marksystemobject sp_EstimatedTablesRowSize ;

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