UDF: Estimating the size of a table
In database planning and design it is essential to plan out how much HD space you are going to need to store your data. If you use BOL and do a search for "Estimating Table Size" you get three articles:
- Estimating the size of a table
- Estimating the size of a table with a Clustered Index
- Estimating the size of a table without a Clustered Index
These articles cover step by step how to estimate how much space your table's data and indexes are going to utilize. The problem; they aren't translated into T-SQL so the calculation is manual.
The UDFs installed with this script automate the calculation. All you need to do is create your table and its indexes and execute the fnTableSize function which returns the number of bytes used for the table's data, the table's indexes, and the total table size.
Function usage:
Select * from dbo.ftTableSize (@vcTableName='[Name of table]',@rTableRows=[Number of rows to be stored],@rVarPercentUsed=[Percentage of variable data types filled*])
* @rVarPercentUsed refers to the amount of variable data that will be populated if a varchar(100) contains 50 characters the @rVarPercentUsed is 50.
-- Example:
IF EXISTS(Select * from sysobjects where id = OBJECT_ID(N'tblTest'))
DROP TABLE tblTest
GO
CREATE TABLE tblTest (iRecId INT IDENTITY(1,1) PRIMARY KEY, vcVarValue VARCHAR(200),iIntValue INT,dtDateValue DATETIME,txTextValue TEXT)
CREATE UNIQUE NONCLUSTERED INDEX idx1_tblTest ON tblTest (iIntValue,dtDateValue)
GO
Select * from dbo.fnTableSize ('tblTest',1000000,45)
-- OR
Select vcTableName
,rTableRows
,rDataSize/1000000 rDataSize_MB
,rIndexSize/1000000 rIndexSize_MB
,rTableSize/1000000 rTableSize_MB
from dbo.fnTableSize ('tblTest',1000000,45)
Output results are:
vcTableName rTableRows rDataSize rIndexSize rTableSize
-------------------------------------- ------------------------ ------------------------ ------------------------
tb
-- This is an aid in estimating, the accuracy of this script is not guarenteed or implied.
IF EXISTS (Select * from sysobjects where id = OBJECT_ID(N'fnTableDataSize'))
DROP FUNCTION fnTableDataSize
GO
CREATE FUNCTION dbo.fnTableDataSize (@vcTableName VARCHAR(255),@rTableRows REAL,@rVarPercentageUsed REAL)
RETURNS REAL
AS
BEGIN
SET @rVarPercentageUsed = @rVarPercentageUsed / 100
IF EXISTS(Select * from sysobjects where id = OBJECT_ID(@vcTableName))
BEGIN
DECLARE @rFixedColumns REAL
DECLARE @rVariableColumns REAL
DECLARE @rTotalColumns REAL
DECLARE @rFixedDataSize REAL
DECLARE @rMaxVarSize REAL
DECLARE @rVarDataSize REAL
DECLARE @rNullBitmap REAL
DECLARE @rBytesPerRow REAL
DECLARE @rRowsPerPage REAL
DECLARE @rNumPages REAL
DECLARE @rTableBytes REAL
DECLARE @rTableKBytes REAL
DECLARE @rTableMBytes REAL
DECLARE @rTableGBytes REAL
DECLARE @rFreeRowsPerPage REAL
DECLARE @rFillFactor REAL
SET @rFixedColumns = (select count(*) from syscolumns sc INNER JOIN systypes st ON sc.xtype = st.xtype Where sc.id = OBJECT_ID(@vcTableName) and st.variable = 0)
SET @rFixedDataSize = (select sum(sc.length) from syscolumns sc INNER JOIN systypes st ON sc.xtype = st.xtype Where sc.id = OBJECT_ID(@vcTableName) and st.variable = 0)
SET @rNullBitmap = ROUND(2 + ((@rFixedColumns + 7) / 8),0,1)
SET @rVariableColumns = (select count(*) from syscolumns sc INNER JOIN systypes st ON sc.xtype = st.xtype Where sc.id = OBJECT_ID(@vcTableName) and st.variable = 1)
SET @rMaxVarSize = (Select SUM(sc.length) from syscolumns sc INNER JOIN systypes st ON sc.xtype = st.xtype where sc.id = OBJECT_ID(@vcTableName) and st.Variable = 1)
IF @rVariableColumns = 0
SET @rVarDataSize = 0
ELSE
SET @rVarDataSize = (2 + (@rVariableColumns * 2) + @rMaxVarSize) * @rVarPercentageUsed
SET @rBytesPerRow = @rFixedDataSize + @rVarDataSize + @rNullBitmap + 4
IF 8096 / (@rBytesPerRow + 2) < 1
SET @rRowsPerPage = CEILING(8096 / (@rBytesPerRow + 2))
ELSE
SET @rRowsPerPage = FLOOR(8096 / (@rBytesPerRow + 2))
SET @rFillFactor = 100
IF EXISTS(select * from sysindexes where id = OBJECT_ID(@vcTableName) and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsClustered') = 1)
SET @rFillFactor = (select INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IndexFillFactor') from sysindexes where id = OBJECT_ID(@vcTableName) and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsClustered') = 1)
IF @rFillFactor = 0 SET @rFillFactor = 100
SET @rFreeRowsPerPage = CEILING(8096 * ((100 - @rFillFactor) / 100) / (@rBytesPerRow + 2))
SET @rNumPages = CEILING(@rTableRows / (@rRowsPerPage - @rFreeRowsPerPage))
SET @rTableBytes = 8192 * @rNumPages
END
ELSE
BEGIN
RETURN -1
END
RETURN @rTableBytes
END
GO
IF EXISTS(Select * from sysobjects where id = OBJECT_ID(N'fnTableIndexSize'))
DROP FUNCTION fnTableIndexSize
GO
CREATE FUNCTION dbo.fnTableIndexSize (@vcTableName VARCHAR(255),@rDataSize REAL,@rTableRows REAL,@rVarPercentageUsed REAL)
RETURNS REAL
AS
BEGIN
DECLARE @vcIndexName VARCHAR(255)
DECLARE @rFixedColumns REAL
DECLARE @rFixedCKeySize REAL
DECLARE @rNullBitmap REAL
DECLARE @rVarColumns REAL
DECLARE @rMaxVarSize REAL
DECLARE @rVarCKeySize REAL
DECLARE @rCIndexRowSize REAL
DECLARE @rCIndexRowsPerPage REAL
DECLARE @rCLevel0 REAL
DECLARE @rCLevel1 REAL
DECLARE @rCLevel2 REAL
DECLARE @rPrevCLevel REAL
DECLARE @rCurCLevel REAL
DECLARE @rCumCLevel REAL
DECLARE @rCIndexPages REAL
DECLARE @tblIndexes TABLE (iRowId INT IDENTITY(1,1),vcIndexName VARCHAR(255))
DECLARE @iRowId INT
DECLARE @iRowCount INT
DECLARE @rNLIndexRowSize REAL
DECLARE @rNLIndexRowsPerPage REAL
DECLARE @rLIndexRowSize REAL
DECLARE @rLIndexRowsPerPage REAL
DECLARE @rLFreeIndexRowsPerPage REAL
DECLARE @rFillFactor REAL
DECLARE @rLLevel0 REAL
DECLARE @rLLevel1 REAL
DECLARE @rLLevel2 REAL
DECLARE @rPrevLLevel REAL
DECLARE @rCurLLevel REAL
DECLARE @rCumLLevel REAL
DECLARE @rLIndexPages REAL
DECLARE @rCIndexBytes REAL
DECLARE @rNIndexBytes REAL
DECLARE @rTotalIndexBytes REAL
DECLARE @rIndexRowSize REAL
DECLARE @rIndexRowsPerPage REAL
DECLARE @rFreeIndexRowsPerPage REAL
DECLARE @rIndexPages REAL
DECLARE @rIndexBytes REAL
SET @rVarPercentageUsed = @rVarPercentageUsed / 100
IF EXISTS(Select * from sysindexes where id = OBJECT_ID(@vcTableName) and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsClustered') = 1)
BEGIN
SET @vcIndexName = (Select name from sysindexes where id = OBJECT_ID(@vcTableName) and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsClustered') = 1)
SET @rFixedColumns = (Select count(*) from sysobjects so
INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc on so.id = sc.id and sc.colorder = sk.colid and si.id = sc.id
Where sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName)
SET @rFixedCKeySize = (Select IsNull(sum(sc.length),0) From sysobjects so
INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 0))
SET @rNullBitmap = ROUND(2 + ((@rFixedColumns + 7) / 8),0,1)
SET @rVarColumns = (Select count(*) from sysobjects so INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 1))
SET @rMaxVarSize = (Select IsNull(sum(length),0) From sysobjects so INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 1))
IF @rVarColumns = 0
SET @rVarCKeySize = 0
ELSE
SET @rVarCKeySize = (2 + (@rVarColumns * 2) + @rMaxVarSize) * @rVarPercentageUsed
SET @rCIndexRowSize = @rFixedCKeySize + @rVarCKeySize + @rNullBitmap + 1 + 8
IF (8096 / (@rCIndexRowSize + 2)) < 1
SET @rCIndexRowsPerPage = CEILING(8096 / (@rCIndexRowSize + 2))
ELSE
SET @rCIndexRowsPerPage = FLOOR(8096 / (@rCIndexRowSize + 2))
SET @rCLevel0 = CEILING((@rDataSize / 8192) / @rCIndexRowsPerPage)
SET @rCLevel1 = CEILING(@rCLevel0 / @rCIndexRowsPerPage)
SET @rCLevel2 = CEILING(@rCLevel1 / @rCIndexRowsPerPage)
SET @rPrevCLevel = @rCLevel2
SET @rCurCLevel = @rPrevCLevel
WHILE @rCurCLevel > 1
BEGIN
SET @rCurCLevel = CEILING(@rPrevCLevel / @rCIndexRowsPerPage)
SET @rCumCLevel = IsNull(@rCumCLevel,0) + @rCurCLevel
SET @rPrevCLevel = @rCurCLevel
END
SET @rCIndexPages = @rCLevel0 + @rCLevel1 + @rCLevel2 + IsNull(@rCumCLevel,0)
SET @rCIndexBytes = 8192 * @rCIndexPages
INSERT INTO @tblIndexes Select name from sysindexes where id = OBJECT_ID(@vcTableName) and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsClustered') = 0 and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsHypothetical') = 0 and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsAutoStatistics') = 0
SET @iRowId = @@ROWCOUNT
WHILE @iRowId > 0
BEGIN
SET @vcIndexName = (Select vcIndexName from @tblIndexes where iRowId = @iRowId)
SET @rFixedColumns = (Select count(*) from sysobjects so
INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc on so.id = sc.id and sc.colorder = sk.colid and si.id = sc.id
Where sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName)
SET @rFixedCKeySize = (Select IsNull(sum(sc.length),0) From sysobjects so
INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 0))
SET @rNullBitmap = ROUND(2 + ((@rFixedColumns + 7) / 8 ),0,1)
SET @rVarColumns = (Select count(*) from sysobjects so INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 1))
SET @rMaxVarSize = (Select IsNull(sum(length),0) From sysobjects so INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 1))
IF @rVarColumns = 0
SET @rVarCKeySize = 0
ELSE
SET @rVarCKeySize = (2 + (@rVarColumns * 2) + @rMaxVarSize) * @rVarPercentageUsed
SET @rNLIndexRowSize = @rFixedCKeySize + @rVarCKeySize + @rNullBitmap + 1 + 8
IF 8096 / (@rNLIndexRowSize + 2) < 1
SET @rNLIndexRowsPerPage = CEILING(8096 / (@rNLIndexRowSize + 2))
ELSE
SET @rNLIndexRowsPerPage = FLOOR(8096 / (@rNLIndexRowSize + 2))
SET @rLIndexRowSize = @rCIndexRowSize + @rFixedCKeySize + @rVarCKeySize + @rNullBitmap + 1
IF 8096 / (@rLIndexRowSize + 2) < 1
SET @rLIndexRowsPerPage = CEILING(8096 / (@rLIndexRowSize + 2))
ELSE
SET @rLIndexRowsPerPage = FLOOR(8096 / (@rLIndexRowSize + 2))
SET @rFillFactor = 100
IF EXISTS(select * from sysindexes where id = OBJECT_ID(@vcTableName) and name = @vcIndexName)
SET @rFillFactor = (select INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IndexFillFactor') from sysindexes where id = OBJECT_ID(@vcTableName) and name = @vcIndexName)
IF @rFillFactor = 0 SET @rFillFactor = 100
IF 8096 * ((100 - @rFillFactor) / 100) / @rLIndexRowsPerPage < 1
SET @rLFreeIndexRowsPerPage = CEILING(8096 * ((100 - @rFillFactor) / 100) / @rLIndexRowsPerPage)
ELSE
SET @rLFreeIndexRowsPerPage = FLOOR(8096 * ((100 - @rFillFactor) / 100) / @rLIndexRowsPerPage)
SET @rLLevel0 = CEILING(@rTableRows / (@rLIndexRowsPerPage - @rLFreeIndexRowsPerPage))
SET @rLLevel1 = CEILING(@rLLevel0 / @rNLIndexRowsPerPage)
SET @rLLevel2 = CEILING(@rLLevel1 / @rNLIndexRowsPerPage)
SET @rPrevLLevel = @rLLevel2
SET @rCurLLevel = @rPrevLLevel
WHILE @rCurLLevel > 1
BEGIN
SET @rCurLLevel = CEILING(@rPrevLLevel / @rNLIndexRowsPerPage)
SET @rCumLLevel = IsNull(@rCumLLevel,0) + @rCurLLevel
SET @rPrevLLevel = @rCurLLevel
END
SET @rLIndexPages = @rLLevel0 + @rLLevel1 + @rLLevel2 + IsNull(@rCumLLevel,0)
SET @rNIndexBytes = IsNull(@rNIndexBytes,0) + (8192 * @rLIndexPages)
SET @iRowId = @iRowId - 1
END
SET @rTotalIndexBytes = @rNIndexBytes + @rCIndexBytes
END
ELSE
BEGIN
INSERT INTO @tblIndexes Select name from sysindexes where id = OBJECT_ID(@vcTableName) and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsClustered') = 0 and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsHypothetical') = 0 and INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IsAutoStatistics') = 0
SET @iRowId = @@ROWCOUNT
WHILE @iRowId > 0
BEGIN
SET @vcIndexName = (Select vcIndexName from @tblIndexes where iRowId = @iRowId)
SET @rFixedColumns = (Select count(*) from sysobjects so
INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc on so.id = sc.id and sc.colorder = sk.colid and si.id = sc.id
Where sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName)
SET @rFixedCKeySize = (Select IsNull(sum(sc.length),0) From sysobjects so
INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 0))
SET @rNullBitmap = ROUND(2 + ((@rFixedColumns + 7) / 8 ),0,1)
SET @rVarColumns = (Select count(*) from sysobjects so INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 1))
SET @rMaxVarSize = (Select IsNull(sum(length),0) From sysobjects so INNER JOIN sysindexes si ON so.id = si.id
INNER JOIN sysindexkeys sk ON so.id = sk.id and sk.indid = si.indid
INNER JOIN syscolumns sc ON sc.id = so.id and sc.colorder = sk.colid and si.id = sc.id
WHERE sc.id = OBJECT_ID(@vcTableName)
and si.name = @vcIndexName
and sc.xtype in (select xtype from systypes where variable = 1))
IF @rVarColumns = 0
SET @rVarCKeySize = 0
ELSE
SET @rVarCKeySize = (2 + (@rVarColumns * 2) + @rMaxVarSize) * @rVarPercentageUsed
SET @rIndexRowSize = @rFixedCKeySize + @rVarCKeySize + @rNullBitmap + 1 + 8
IF 8096 / (@rIndexRowSize + 2) < 1
SET @rIndexRowsPerPage = CEILING(8096 / (@rIndexRowSize + 2))
ELSE
SET @rIndexRowsPerPage = FLOOR(8096 / (@rIndexRowSize + 2))
SET @rFillFactor = 100
IF EXISTS(select * from sysindexes where id = OBJECT_ID(@vcTableName) and name = @vcIndexName)
SET @rFillFactor = (select INDEXPROPERTY(OBJECT_ID(@vcTableName),name,'IndexFillFactor') from sysindexes where id = OBJECT_ID(@vcTableName) and name = @vcIndexName)
IF @rFillFactor = 0 SET @rFillFactor = 100
IF 8096 * ((100 - @rFillFactor) / 100) / @rIndexRowsPerPage < 1
SET @rFreeIndexRowsPerPage = CEILING(8096 * ((100 - @rFillFactor) / 100) / @rIndexRowsPerPage)
ELSE
SET @rFreeIndexRowsPerPage = FLOOR(8096 * ((100 - @rFillFactor) / 100) / @rIndexRowsPerPage)
SET @rCLevel0 = CEILING(@rTableRows / (@rIndexRowsPerPage - @rFreeIndexRowsPerPage))
SET @rCLevel1 = CEILING(@rCLevel0 / @rIndexRowsPerPage)
SET @rPrevCLevel = @rCLevel1
SET @rCurCLevel = @rPrevCLevel
WHILE @rCurCLevel > 1
BEGIN
SET @rCurCLevel = CEILING(@rPrevCLevel / @rIndexRowsPerPage)
SET @rCumCLevel = IsNull(@rCumCLevel,0) + @rCurCLevel
SET @rPrevCLevel = @rCurCLevel
END
SET @rIndexPages = @rCLevel0 + @rCLevel1 + @rCLevel2 + IsNull(@rCumCLevel,0)
SET @rIndexBytes = 8192 * @rIndexPages
SET @rTotalIndexBytes = IsNull(@rTotalIndexBytes,0) + @rIndexBytes
SET @iRowId = @iRowId - 1
END
END
RETURN @rTotalIndexBytes
END
GO
IF EXISTS(Select * from sysobjects where id = OBJECT_ID('fnTableSize'))
DROP FUNCTION fnTableSize
GO
CREATE FUNCTION dbo.fnTableSize (@vcTableName VARCHAR(255),@rTableRows REAL = 0,@rVarPercentUsed REAL)
RETURNS @tblTableSize TABLE (vcTableName VARCHAR(255),rTableRows REAL,rDataSize REAL,rIndexSize REAL,rTableSize REAL)
AS
BEGIN
DECLARE @rDataSize REAL
DECLARE @rIndexSize REAL
DECLARE @rTableSize REAL
SET @rDataSize = (select dbo.fnTableDataSize(@vcTableName,@rTableRows,@rVarPercentUsed))
SET @rIndexSize = (select dbo.fnTableIndexSize(@vcTableName,@rDataSize,@rTableRows,@rVarPercentUsed))
SET @rTableSize = (@rDataSize + @rIndexSize)
INSERT INTO @tblTableSize (vcTableName,rTableRows,rDataSize,rIndexSize,rTableSize)
VALUES (@vcTableName,@rTableRows,@rDataSize,@rIndexSize,@rTableSize)
RETURN
END
GO 
