USE db_main;
GO
SET NOCOUNT ON;

-- Rebuild or reorganize indexes based on their fragmentation levels
DECLARE @work_to_do TABLE (
    objectid INT
    , indexid INT
    , pagedensity FLOAT
    , fragmentation FLOAT
    , numrows INT
)

DECLARE @objectid INT;
DECLARE @indexid INT;
DECLARE @schemaname nvarchar(130);
DECLARE @objectname nvarchar(130);
DECLARE @indexname nvarchar(130);
DECLARE @numrows INT
DECLARE @density FLOAT;
DECLARE @fragmentation FLOAT;
DECLARE @command nvarchar(4000);
DECLARE @fillfactorset bit
DECLARE @numpages INT

-- Select indexes that need to be defragmented based on the following
-- * Page density is low
-- * External fragmentation is high in relation to index size
PRINT 'Estimating fragmentation: Begin. ' + CONVERT(nvarchar, getdate(), 121)
INSERT @work_to_do
SELECT
    f.object_id
    , index_id
    , avg_page_space_used_in_percent
    , avg_fragmentation_in_percent
    , record_count
FROM
    sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL , NULL, 'SAMPLED') AS f
WHERE
    (f.avg_page_space_used_in_percent < 85.0 AND f.avg_page_space_used_in_percent/100.0 * page_count < page_count - 1)
    OR (f.page_count > 50 AND f.avg_fragmentation_in_percent > 15.0)
    OR (f.page_count > 10 AND f.avg_fragmentation_in_percent > 80.0)

PRINT 'Number of indexes to rebuild: ' + CAST(@@ROWCOUNT AS nvarchar(20))

PRINT 'Estimating fragmentation: End. ' + CONVERT(nvarchar, getdate(), 121)

SELECT @numpages = SUM(ps.used_page_count)
FROM
    @work_to_do AS fi
    INNER JOIN sys.indexes AS i ON fi.objectid = i.object_id AND fi.indexid = i.index_id
    INNER JOIN sys.dm_db_partition_stats AS ps ON i.object_id = ps.object_id AND i.index_id = ps.index_id

-- Declare the cursor for the list of indexes to be processed.
DECLARE curIndexes CURSOR FOR SELECT * FROM @work_to_do

-- Open the cursor.
OPEN curIndexes

-- Loop through the indexes
WHILE (1=1)
BEGIN
    FETCH NEXT FROM curIndexes
    INTO @objectid, @indexid, @density, @fragmentation, @numrows;
    IF @@FETCH_STATUS < 0 BREAK;

    SELECT
        @objectname = QUOTENAME(o.name)
        , @schemaname = QUOTENAME(s.name)
    FROM
        sys.objects AS o
        INNER JOIN sys.schemas AS s ON s.schema_id = o.schema_id
    WHERE
        o.object_id = @objectid;

    SELECT
        @indexname = QUOTENAME(name)
        , @fillfactorset = CASE fill_factor WHEN 0 THEN 0 ELSE 1 END
    FROM
        sys.indexes
    WHERE
        object_id = @objectid AND index_id = @indexid;

    IF ((@density BETWEEN 75.0 AND 85.0) AND @fillfactorset = 1) OR (@fragmentation < 30.0)
        SET @command = N'ALTER INDEX ' + @indexname + N' ON ' + @schemaname + N'.' + @objectname + N' REORGANIZE';
    ELSE IF @numrows >= 5000 AND @fillfactorset = 0
        SET @command = N'ALTER INDEX ' + @indexname + N' ON ' + @schemaname + N'.' + @objectname + N' REBUILD WITH (FILLFACTOR = 90)';
    ELSE
        SET @command = N'ALTER INDEX ' + @indexname + N' ON ' + @schemaname + N'.' + @objectname + N' REBUILD';
    PRINT CONVERT(nvarchar, getdate(), 121) + N' Executing: ' + @command;
    EXEC (@command);
    PRINT CONVERT(nvarchar, getdate(), 121) + N' Done.';
END

-- Close and deallocate the cursor.
CLOSE curIndexes;
DEALLOCATE curIndexes;


IF EXISTS (SELECT * FROM @work_to_do)
BEGIN
    PRINT 'Estimated number of pages in fragmented indexes: ' + CAST(@numpages AS nvarchar(20))
    SELECT @numpages = @numpages - SUM(ps.used_page_count)
    FROM
        @work_to_do AS fi
        INNER JOIN sys.indexes AS i ON fi.objectid = i.object_id AND fi.indexid = i.index_id
        INNER JOIN sys.dm_db_partition_stats AS ps ON i.object_id = ps.object_id AND i.index_id = ps.index_id

    PRINT 'Estimated number of pages freed: ' + CAST(@numpages AS nvarchar(20))
END
GO


--Update all statistics
PRINT 'Updating all statistics.' + CONVERT(nvarchar, getdate(), 121)
EXEC sp_updatestats
PRINT 'Done updating statistics.' + CONVERT(nvarchar, getdate(), 121)
GO