Data compression in SQL Server can definitely go a long way in saving storage space, as well as improve performance. It can especially be significant in very large databases. But in certain scenarios it can actually cause more harm than good, and it’s important to identify these scenarios.
I wrote this script which performs compression savings estimation checks for an ENTIRE database. Yeah there are plenty such scripts out there already, but there’s something in particular that they all seem to be missing, and that is the ability to actually generate the relevant remediation commands for you. After all, ain’t nobody got time for writing all those “ALTER TABLE/INDEX” commands themselves!
This is why I created the T-SQL script below. Check out the “messages” tab once the script completes execution, to find the resulting remediation commands. In addition, you will also get a query result with full details.
The script also performs various checks to determine whether PAGE or ROW compression type would be more beneficial (based on stuff such as range scans vs. updates percentage, difference in compression savings, etc.). It has several parameters at the top to control various thresholds and behaviors, so that you could fine tune it for your specific database.
The default values for all parameters should fit most use cases, but you can still customize them if you have to. I’ve added comments next to each parameter with more details.
Speaking of which, I added a bunch of comments all over the script, and tried my best to make it as concise and reader-friendly as possible. But, if something is still isn’t clear in the script, please let me know (either at the comments section here or at the GitHub Gist), and I’ll do my best to clarify.
A few important notes first
The script performs the check for an entire database based on what’s specified in the @DatabaseName parameter. So don’t forget to change the @DatabaseName parameter to the one you actually want to check (or leave it as NULL to check the database you’re currently connected to).
BE MINDFUL IN PRODUCTION ENVIRONMENTS !
Running this script may take a very long time on databases with large tables, and significant IO and CPU stress may be noticeable. Ironically though, that is usually where you’ll have the biggest benefit to compression.
Schema-level locks may be held for a while per each table, and will possibly block other sessions performing DDL operations (ALTER, DROP, TRUNCATE etc.).
One extra important thing to remember is that this script uses the built-in data compression savings estimation procedure (sp_estimate_data_compression_savings) per each table and compression type (PAGE and ROW). This procedure copies 5% of your table to TempDB and compresses it there. This means that if you have an extremely huge table, it could cause TempDB to significantly inflate in size, which might fill out the storage disk it’s on, or reach its max size (both of which will make your SQL Server unresponsive!).
This is why I’ve added a few cautionary checks and additional threshold parameters, in order to avoid such scenarios: Specifically, @FeasibilityCheckOnly, @MaxSizeMBForActualCheck and @TempDBSpaceUsageThresholdPercent. The parameter @FeasibilityCheckOnly in particular is used to determine whether you want to run sp_estimate_data_compression_savings, or you just want to do a “basic” check (which shouldn’t cause any overheads or major issues) to find possible candidates for compression.
In general, if you want to run this script in a production environment, be sure to do it during low-traffic hours, and make sure you have enough free disk space on the TempDB drive.
The Script:
Click here to get it from my GitHub Gists.
| —————————————————————– | |
| ——— Ultimate Compression Savings Estimation Check ——— | |
| —————————————————————– | |
| — Author: Eitan Blumin | https://www.eitanblumin.com | |
| — Create Date: 2019-12-08 | |
| — Source: http://bit.ly/SQLCompressionEstimation | |
| — Full Link: https://gist.github.com/EitanBlumin/85cf620f7267b234d677f9c3027fb7ce | |
| — GitHub Repo: https://github.com/MadeiraData/MadeiraToolbox/blob/master/Utility%20Scripts/ultimate_compression_savings_estimation_whole_database.sql | |
| — Blog: https://eitanblumin.com/2020/02/18/ultimate-compression-savings-estimation-script-entire-database/ | |
| —————————————————————– | |
| — Description: | |
| — ———— | |
| — This script performs compression savings estimation check for both PAGE and ROW | |
| — compression for an ENTIRE DATABASE. | |
| — For each index which passes the check, a corresponding ALTER INDEX command | |
| — is printed for you to use in order to apply the compression. | |
| — The script also compares the results of the PAGE and ROW estimations and automatically | |
| — selects the one with the better savings as the command to print, based on the provided thresholds. | |
| — This script uses mathematical rounding functions FLOOR and CEILING in a manner which makes it more "cautious". | |
| — | |
| — Some of the algorithms in this script were adapted from the following resources: | |
| — https://www.sqlservercentral.com/blogs/introducing-what_to_compress-v2 | |
| — https://github.com/microsoft/tigertoolbox/tree/master/Evaluate-Compression-Gains | |
| — https://github.com/microsoft/azure-sql-tips | |
| —————————————————————– | |
| — Change Log: | |
| — ———– | |
| — 2021-09-06 – added @ResumableRebuild parameter | |
| — 2021-09-01 – some minor bug fixes and code quality fixes | |
| — 2021-02-02 – added SET NOCOUNT, QUOTED_IDENTIFIER, ARITHABORT, XACT_ABORT ON settings | |
| — 2021-01-17 – added cautionary parameters to stop/pause execution if CPU utilization is too high | |
| — 2021-01-17 – added optional cautionary parameters controlling allowed/forbidden execution window | |
| — 2021-01-17 – made some changes to threshold parameters based on partition stats (adapted from Azure-SQL-Tips) | |
| — 2021-01-05 – added informative message about current TempDB available space | |
| — 2020-12-06 – added @MaximumUpdatePctAsInfrequent and @MinimumScanPctForComparison parameters | |
| — 2020-12-01 – output remediation script is now idempotent; fixed recommendations in resultset to match actual remediation script | |
| — 2020-09-30 – added @MaxDOP parameter | |
| — 2020-09-06 – added support for readable secondaries; added MAXDOP 1 for the query from operational stats to avoid access violation bug | |
| — 2020-03-30 – added filter to ignore indexes and tables with unsupported LOB/FILESTREAM columns | |
| — 2020-03-16 – added informational and status messages in output script | |
| — 2020-03-15 – tweaked default parameter values a bit; added server uptime message | |
| — 2020-02-26 – added best guess for unknown compression recommendations; improved performance for DBs with many objects | |
| — 2020-02-19 – added support for Azure SQL DB | |
| — 2020-02-18 – cleaned the code a bit and fixed some bugs | |
| — 2020-02-17 – added specific database support; adjusted tabs to match github standard; added compatibility checks | |
| — 2020-02-16 – added threshold parameters; additional checks based on partition stats and operational stats | |
| — 2019-12-09 – added ONLINE rebuild option | |
| — 2019-12-24 – flipped to traditional ratio calculation; added READ UNCOMMITTED isolation level; added minimum difference thresholds for PAGE vs. ROW considerations | |
| —————————————————————– | |
| — | |
| — IMPORTANT !!! | |
| — ————- | |
| — | |
| — 1. Don't forget to change the @DatabaseName parameter value to the one you want to check. | |
| — | |
| — 2. BE MINDFUL IN PRODUCTION ENVIRONMENTS ! | |
| — | |
| — – If you want to be extra careful, run this script with @FeasibilityCheckOnly set to 1. This will perform only basic checks for compression candidates | |
| — based on usage and operational stats only, without running [sp_estimate_data_compression_savings]. | |
| — | |
| — – Running this script with @FeasibilityCheckOnly = 0 may take a very long time on big databases with many tables, and significant IO + CPU stress may be noticeable. | |
| — | |
| — – Schema-level locks may be held for a while per each table, and will possibly block other sessions performing DDL operations. | |
| — | |
| — – This script uses [sp_estimate_data_compression_savings] which copies 5 % of your data into TempDB and compresses it there. | |
| — If you have very large tables, you must be very careful not to fill out the disk. | |
| — Please use the following cautionary threshold parameters to avoid such scenarios: @MaxSizeMBForActualCheck, @TempDBSpaceUsageThresholdPercent | |
| —————————————————————– | |
| — Parameters: | |
| — ———– | |
| DECLARE | |
| — Choose what to check: | |
| @DatabaseName SYSNAME = NULL — Specify the name of the database to check. If NULL, will use current. | |
| ,@FeasibilityCheckOnly BIT = 1 — If 1, will only check for potential compression candidates, without using sp_estimate_data_compression_savings and without generating remediation scripts | |
| ,@CheckPerPartition BIT = 0 — If 1, will perform separate estimation checks per partition | |
| ,@MinimumSizeMB INT = 256 — Minimum table/partition size in MB in order to perform estimation checks on it | |
| — Cautionary thresholds: | |
| ,@MaxSizeMBForActualCheck INT = NULL — If a table/partition is bigger than this size (in MB), then sp_estimate_data_compression_savings will NOT be executed for it. If set to NULL, then use available TempDB space instead | |
| ,@TempDBSpaceUsageThresholdPercent INT = 60 — A percentage number between 1 and 100, representing how much of the disk space available to TempDB is allowed to be used for the estimation checks | |
| — Cautionary parameters to stop/pause execution if CPU utilization is too high (this affects both the estimation check and the rebuild script): | |
| ,@MaximumCPUPercentForRebuild INT = 80 — Maximum average CPU utilization to allow rebuild. Set to NULL to ignore. | |
| ,@SamplesToCheckAvgForCPUPercent INT = 10 — Number of CPU utilization percent samples to check and average out | |
| ,@MaximumTimeToWaitForCPU DATETIME = '00:10:00' — Maximum time to continously wait for CPU utilization to drop below threshold, before cancelling execution (HH:MM:SS.MS format). Set to NULL to wait forever. | |
| — Optional cautionary parameters controlling allowed execution window (server clock) | |
| — You can think of this as your "maintenance window" (24hour based. for example, between 0 and 4): | |
| ,@AllowedRuntimeHourFrom INT = NULL — If not NULL, will specify minimum hour of day during which rebuilds are allowed | |
| ,@AllowedRuntimeHourTo INT = NULL — If not NULL, will specify maximum hour of day during which rebuilds are allowed | |
| — Optional cautionary parameters controlling forbidden execution window (server clock) | |
| — You can think of this as your "business hours" (24hour based. for example, between 6 and 22): | |
| ,@NotAllowedRuntimeHourFrom INT = 6 — If not NULL, will specify minimum time of day during which rebuilds are forbidden | |
| ,@NotAllowedRuntimeHourTo INT = 22 — If not NULL, will specify maximum time of day during which rebuilds are forbidden | |
| — Threshold parameters controlling recommendation algorithms based on partition stats: | |
| ,@MinimumCompressibleDataPercent INT = 45 — Minimum percent of compressible in-row data, in order to consider any compression | |
| ,@MaximumUpdatePctAsInfrequent INT = 10 — Maximum percent of updates for all operations to consider as "infrequent updates" | |
| ,@MinimumScanPctForComparison INT = 5 — Minimum percent of range scans before considering to compare between update and scan percentages | |
| ,@MinimumScanPctForPage INT = 40 — Minimum percent of scans when comparing to update percent, to deem PAGE compression preferable (otherwise, ROW compression will be preferable) | |
| ,@MaximumUpdatePctForPage INT = 40 — Maximum percent of updates when comparing to scan percent, to deem PAGE compression preferable | |
| ,@MaximumUpdatePctForRow INT = 60 — Maximum percent of updates when comparing to scan percent, to deem ROW compression preferable | |
| — Threshold parameters controlling recommendation algorithms based on savings estimation check: | |
| ,@CompressionRatioThreshold FLOAT = 45 — Number between 0 and 100 representing the minimum compressed data ratio, relative to current size, for which a check will pass | |
| ,@CompressionSizeSavedMBThreshold FLOAT = 200 — Minimum estimated saved space in MB resulting from compression (affects both PAGE and ROW compressions) | |
| ,@MinimumRatioDifferenceForPage FLOAT = 10 — Minimum difference in percentage between ROW and PAGE compression types, in order to deem PAGE compression preferable | |
| ,@MinimumSavingsMBDifferenceForPage FLOAT = 40 — Minimum difference in saved space in MB between ROW and PAGE compression types, in order to deem PAGE compression preferable | |
| — Parameters controlling the structure of output scripts: | |
| ,@OnlineRebuild BIT = 1 — If 1, will generate REBUILD commands with the ONLINE option turned on | |
| ,@ResumableRebuild BIT = 0 — If 1, will generate REBUILD commands with the RESUMABLE option turned on (SQL 2019 and newer only) | |
| ,@SortInTempDB BIT = 1 — If 1, will generate REBUILD commands with the SORT_IN_TEMPDB option turned on | |
| ,@MaxDOP INT = NULL — If not NULL, will add a MaxDOP option accordingly. Set to 1 to prevent parallelism and reduce workload. | |
| ——————————————————————— | |
| — DO NOT CHANGE ANYTHING BELOW THIS LINE — | |
| ——————————————————————— | |
| SET NOCOUNT, ARITHABORT, XACT_ABORT ON; | |
| SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; | |
| — Variable declaration | |
| DECLARE @CMD NVARCHAR(MAX), @AvailableTempDBSpaceMB INT, @ErrMsg NVARCHAR(MAX) | |
| DECLARE @CurrDB SYSNAME, @Schema SYSNAME, @Table SYSNAME, @ObjectId INT, @IndexId INT, @IndexName SYSNAME, @Partition INT, @CompressionType VARCHAR(4), @EstimationCheckRecommended BIT, @TotalSizeMB INT, @InRowPercent INT, @ScanPercent INT, @UpdatePercent INT | |
| DECLARE @Results AS TABLE ([object_name] SYSNAME NOT NULL, [schema_name] SYSNAME NOT NULL, index_id int NULL, partition_number int NULL, size_w_current_compression_KB float NULL, size_w_requested_compression_KB float NULL, sample_size_current_KB int NULL, sample_size_requested_KB int NULL) | |
| DECLARE @RebuildOptions NVARCHAR(MAX), @ChecksSkipped BIT | |
| — Compatibility checks | |
| SELECT @ErrMsg = ISNULL(@ErrMsg + ', ', N'Sorry, this SQL Server version is not supported. Missing object(s): ') + objectname | |
| FROM ( | |
| SELECT objectname = CONVERT(nvarchar(500), 'sys.tables') | |
| UNION ALL SELECT 'sys.dm_os_volume_stats' WHERE CONVERT(varchar(300),SERVERPROPERTY('Edition')) <> 'SQL Azure' | |
| UNION ALL SELECT 'sys.master_files' WHERE CONVERT(varchar(300),SERVERPROPERTY('Edition')) <> 'SQL Azure' | |
| UNION ALL SELECT 'sys.dm_db_index_operational_stats' | |
| UNION ALL SELECT 'sys.dm_db_partition_stats' | |
| UNION ALL SELECT 'sys.sp_estimate_data_compression_savings' | |
| UNION ALL SELECT 'sys.indexes' | |
| UNION ALL SELECT 'sys.partitions') AS t | |
| WHERE OBJECT_ID(objectname) IS NULL; | |
| IF @ErrMsg IS NOT NULL | |
| BEGIN | |
| RAISERROR(@ErrMsg,16,1) | |
| GOTO Quit; | |
| END | |
| — Init local variables and defaults | |
| SET @RebuildOptions = N'' | |
| IF @ResumableRebuild = 1 SET @OnlineRebuild = 1; | |
| IF @OnlineRebuild = 1 SET @RebuildOptions = @RebuildOptions + N', ONLINE = ON' | |
| IF @ResumableRebuild = 1 SET @RebuildOptions = @RebuildOptions + N', RESUMABLE = ON' | |
| IF @SortInTempDB = 1 SET @RebuildOptions = @RebuildOptions + N', SORT_IN_TEMPDB = ON' | |
| IF @MaxDOP IS NOT NULL SET @RebuildOptions = @RebuildOptions + N', MAXDOP = ' + CONVERT(nvarchar(4000), @MaxDOP) | |
| SET @ChecksSkipped = 0; | |
| SET @FeasibilityCheckOnly = ISNULL(@FeasibilityCheckOnly, 1) | |
| — Validate mandatory percentage parameters | |
| SELECT @ErrMsg = ISNULL(@ErrMsg + CHAR(10), N'Invalid parameter(s): ') + CONVERT(nvarchar(max), N'' + VarName + N' must be a value between 1 and 100') | |
| FROM | |
| (VALUES | |
| ('@MinimumCompressibleDataPercent',@MinimumCompressibleDataPercent) | |
| ,('@MinimumScanPctForPage',@MinimumScanPctForPage) | |
| ,('@MaximumUpdatePctForPage',@MaximumUpdatePctForPage) | |
| ,('@MaximumUpdatePctForRow',@MaximumUpdatePctForRow) | |
| ,('@TempDBSpaceUsageThresholdPercent',@TempDBSpaceUsageThresholdPercent) | |
| ,('@CompressionRatioThreshold',@CompressionRatioThreshold) | |
| ,('@MinimumRatioDifferenceForPage',@MinimumRatioDifferenceForPage) | |
| ,('@MaximumUpdatePctAsInfrequent',@MaximumUpdatePctAsInfrequent) | |
| ,('@MinimumScanPctForComparison',@MinimumScanPctForComparison) | |
| ,('@MaximumCPUPercentForRebuild',ISNULL(@MaximumCPUPercentForRebuild,100)) | |
| ) AS v(VarName,VarValue) | |
| WHERE VarValue NOT BETWEEN 1 AND 100 OR VarValue IS NULL | |
| OPTION (RECOMPILE); | |
| IF @ErrMsg IS NOT NULL | |
| BEGIN | |
| RAISERROR(@ErrMsg,16,1); | |
| GOTO Quit; | |
| END | |
| — Validate hour-based parameters | |
| SELECT @ErrMsg = ISNULL(@ErrMsg + CHAR(10), N'Invalid parameter(s): ') + CONVERT(nvarchar(max), N'' + VarName + N' must be a value between 0 and 23') | |
| FROM | |
| (VALUES | |
| ('@AllowedRuntimeHourFrom',@AllowedRuntimeHourFrom) | |
| ,('@AllowedRuntimeHourTo',@AllowedRuntimeHourTo) | |
| ,('@NotAllowedRuntimeHourFrom',@NotAllowedRuntimeHourFrom) | |
| ,('@NotAllowedRuntimeHourTo',@NotAllowedRuntimeHourTo) | |
| ) AS v(VarName,VarValue) | |
| WHERE VarValue NOT BETWEEN 0 AND 23 AND VarValue IS NOT NULL | |
| OPTION (RECOMPILE); | |
| IF @ErrMsg IS NOT NULL | |
| BEGIN | |
| RAISERROR(@ErrMsg,16,1); | |
| GOTO Quit; | |
| END | |
| IF @FeasibilityCheckOnly = 0 AND CONVERT(varchar(300),SERVERPROPERTY('Edition')) <> 'SQL Azure' | |
| BEGIN | |
| — Check free space remaining for TempDB | |
| SET @CMD = N'USE tempdb; | |
| SELECT @AvailableTempDBSpaceMB = SUM(ISNULL(available_space_mb,0)) FROM | |
| ( | |
| — Get available space inside data files | |
| SELECT | |
| vs.volume_mount_point | |
| , available_space_mb = SUM(ISNULL(f.size – FILEPROPERTY(f.[name], ''SpaceUsed''),0)) / 128 | |
| + SUM(CASE | |
| — If auto growth is disabled | |
| WHEN f.max_size = 0 THEN 0 | |
| — If remaining growth size is smaller than remaining disk space, use remaining growth size till max size | |
| WHEN f.max_size > 0 AND (f.max_size – f.size) / 128 < (vs.available_bytes / 1024 / 1024) THEN (f.max_size – f.size) / 128 | |
| — Else, do not count available growth for this file | |
| ELSE 0 | |
| END) | |
| FROM sys.master_files AS f | |
| CROSS APPLY sys.dm_os_volume_stats (f.database_id, f.file_id) AS vs | |
| WHERE f.database_id = 2 | |
| AND f.type = 0 | |
| GROUP BY vs.volume_mount_point | |
| UNION ALL | |
| — Get available space on disk for auto-growth | |
| SELECT | |
| vs.volume_mount_point | |
| , available_space_mb = vs.available_bytes / 1024 / 1024 | |
| FROM sys.master_files AS f | |
| CROSS APPLY sys.dm_os_volume_stats (f.database_id, f.file_id) AS vs | |
| WHERE f.database_id = 2 | |
| AND f.type = 0 | |
| — If max size is unlimited, or difference between current size and max size is bigger than available disk space | |
| AND (f.max_size = -1 OR (f.max_size > 0 AND (f.max_size – f.size) / 128 > (vs.available_bytes / 1024 / 1024))) | |
| GROUP BY vs.volume_mount_point, vs.available_bytes | |
| ) AS q OPTION (RECOMPILE);' | |
| EXEC sp_executesql @CMD, N'@AvailableTempDBSpaceMB INT OUTPUT', @AvailableTempDBSpaceMB OUTPUT | |
| — Use @TempDBSpaceUsageThresholdPercent as a cautionary multiplier | |
| SET @AvailableTempDBSpaceMB = @AvailableTempDBSpaceMB * 1.0 * (@TempDBSpaceUsageThresholdPercent / 100.0) | |
| IF @MaxSizeMBForActualCheck > FLOOR(@AvailableTempDBSpaceMB / 0.05) | |
| BEGIN | |
| RAISERROR(N'ALERT: %d percent of available TempDB Disk Space is less than 5 percent of specified @MaxSizeMBForActualCheck (%d). Please adjust @MaxSizeMBForActualCheck and/or @TempDBSpaceUsageThresholdPercent accordingly.', 16, 1, @TempDBSpaceUsageThresholdPercent, @MaxSizeMBForActualCheck); | |
| GOTO Quit; | |
| END | |
| ELSE IF ISNULL(@MaxSizeMBForActualCheck,0) <= 0 — If @MaxSizeMBForActualCheck was not specified, use available TempDB space instead | |
| SET @MaxSizeMBForActualCheck = FLOOR(@AvailableTempDBSpaceMB / 0.05); | |
| RAISERROR(N'— TempDB Free Disk Space: %d MB, max size for check: %d MB',0,1,@AvailableTempDBSpaceMB, @MaxSizeMBForActualCheck) WITH NOWAIT; | |
| END | |
| IF @OnlineRebuild = 1 AND ISNULL(CONVERT(int, SERVERPROPERTY('EngineEdition')),0) NOT IN (3,5,8) | |
| BEGIN | |
| RAISERROR(N'— WARNING: @OnlineRebuild is set to 1, but current SQL edition does not support ONLINE rebuilds.', 0, 1); | |
| END | |
| IF @ResumableRebuild = 1 AND CONVERT(int, (@@microsoftversion / 0x1000000) & 0xff) < 15 | |
| BEGIN | |
| RAISERROR(N'— WARNING: @ResumableRebuild is set to 1, but current SQL version does not support RESUMABLE rebuilds.', 0, 1); | |
| END | |
| DECLARE @ObjectsToCheck AS TABLE | |
| ( | |
| [database_name] SYSNAME NOT NULL, | |
| [schema_name] SYSNAME NOT NULL, | |
| [table_id] int NULL, | |
| [table_name] SYSNAME NULL, | |
| [index_id] INT NULL, | |
| [index_name] SYSNAME NULL, | |
| [partition_number] INT NULL, | |
| size_MB INT NULL, | |
| in_row_percent INT NULL, | |
| range_scans_percent INT NULL, | |
| updates_percent INT NULL | |
| ); | |
| — The following code, making use of @CurrDB variable, is written in a way which would make | |
| — it easier to rewrite so that it can check multiple databases | |
| /* start of potential for-each-db */ | |
| SET @CurrDB = ISNULL(@DatabaseName, DB_NAME()) | |
| PRINT N'————————————————————————————' | |
| PRINT N'————- Compression Savings Estimation Check by Eitan Blumin —————–' | |
| PRINT N'—————- Source: http://bit.ly/SQLCompressionEstimation ——————–' | |
| PRINT N'————————————————————————————' | |
| PRINT N'— for Server: ' + @@SERVERNAME + N' , Database: ' + QUOTENAME(@CurrDB) | |
| PRINT N'————————————————————————————' | |
| DECLARE @SqlStartTime DATETIME, @UpTimeDays INT, @SqlStartTimeString VARCHAR(25); | |
| SELECT @SqlStartTime = sqlserver_start_time FROM sys.dm_os_sys_info; | |
| SET @UpTimeDays = DATEDIFF(dd, @SqlStartTime, GETDATE()) | |
| SET @SqlStartTimeString = CONVERT(varchar(25), @SqlStartTime, 121) | |
| RAISERROR(N'— SQL Server is operational since %s (~%d days)', 0, 1, @SqlStartTimeString, @UpTimeDays) WITH NOWAIT; | |
| — Check whether TempDB is located on same disk as specified database | |
| IF @SortInTempDB = 1 AND CONVERT(varchar(300),SERVERPROPERTY('Edition')) <> 'SQL Azure' | |
| BEGIN | |
| IF EXISTS ( | |
| SELECT fs.volume_mount_point | |
| FROM sys.master_files AS df | |
| CROSS APPLY sys.dm_os_volume_stats(df.database_id, df.file_id) AS fs | |
| WHERE df.type = 0 | |
| AND df.database_id = DB_ID(@CurrDB) | |
| INTERSECT | |
| SELECT fs.volume_mount_point | |
| FROM sys.master_files AS df | |
| CROSS APPLY sys.dm_os_volume_stats(df.database_id, df.file_id) AS fs | |
| WHERE df.type = 0 | |
| AND df.database_id = 2 | |
| ) | |
| RAISERROR(N'— WARNING: @SortInTempDB is set to 1, but TempDB is located on the same disk drive as specified database "%s".', 0, 1, @CurrDB); | |
| END | |
| — Make sure specified database is accessible | |
| IF DB_ID(@CurrDB) IS NULL OR DATABASEPROPERTYEX(@CurrDB, 'Updateability') <> 'READ_WRITE' OR DATABASEPROPERTYEX(@CurrDB, 'Status') <> 'ONLINE' | |
| BEGIN | |
| IF @FeasibilityCheckOnly = 0 OR DB_ID(@CurrDB) IS NULL OR DATABASEPROPERTYEX(@CurrDB, 'Status') <> 'ONLINE' | |
| BEGIN | |
| RAISERROR(N'Database "%s" is not valid for compression estimation check. Please make sure it is accessible and writeable.',16,1,@CurrDB); | |
| GOTO Quit; | |
| END | |
| ELSE | |
| RAISERROR(N'— NOTE: Database "%s" is not writeable. You will not be able to rebuild its indexes here until it is writeable.',10,1,@CurrDB); | |
| END | |
| — Get list of all un-compressed tables/partitions in the specified database | |
| — Use a temp table in order to improve performance for databases with many tables | |
| SET @CMD = N'USE ' + QUOTENAME(@CurrDB) + N'; | |
| IF OBJECT_ID(''tempdb..#objects'') IS NOT NULL DROP TABLE #objects; | |
| CREATE TABLE #objects | |
| ( | |
| [schema_name] SYSNAME | |
| , [object_id] INT | |
| , [table_name] SYSNAME | |
| , [index_id] INT NULL | |
| , [index_name] SYSNAME NULL | |
| , [partition_number] INT NULL | |
| , [size_MB] INT | |
| , [in_row_percent] INT | |
| ); | |
| INSERT INTO #objects | |
| SELECT | |
| OBJECT_SCHEMA_NAME(t.object_id) | |
| , t.object_id | |
| , t.name | |
| , p.index_id | |
| , ix.name | |
| , partition_number = ' + CASE WHEN @CheckPerPartition = 1 THEN N'p.partition_number' ELSE N'NULL' END + N' | |
| , size_MB = CEILING(SUM(ISNULL(sps.in_row_data_page_count,0) + ISNULL(sps.row_overflow_used_page_count,0) + ISNULL(sps.lob_reserved_page_count,0)) / 128.0) | |
| , in_row_percent = ISNULL( | |
| FLOOR(SUM(ISNULL(sps.in_row_data_page_count,0)) * 1.0 | |
| / NULLIF(SUM(ISNULL(sps.in_row_data_page_count,0) + ISNULL(sps.row_overflow_used_page_count,0) + ISNULL(sps.lob_reserved_page_count,0)),0) | |
| * 100.0), 0) | |
| FROM sys.tables AS t WITH(NOLOCK) | |
| INNER JOIN sys.partitions AS p WITH(NOLOCK) ON t.object_id = p.object_id AND p.data_compression = 0 | |
| INNER JOIN sys.indexes AS ix WITH(NOLOCK) ON ix.object_id = t.object_id AND ix.index_id = p.index_id | |
| LEFT JOIN sys.dm_db_partition_stats AS sps WITH(NOLOCK) ON sps.partition_id = p.partition_id | |
| WHERE | |
| — Ignore system objects | |
| t.is_ms_shipped = 0 | |
| AND t.object_id > 255 | |
| AND OBJECT_SCHEMA_NAME(t.object_id) <> ''sys'' | |
| — Ignore indexes or tables with unsupported LOB/FILESTREAM columns | |
| AND NOT EXISTS | |
| ( | |
| SELECT NULL | |
| FROM sys.columns AS c | |
| INNER JOIN sys.types AS t | |
| ON c.system_type_id = t.system_type_id | |
| AND c.user_type_id = t.user_type_id | |
| LEFT JOIN sys.index_columns AS ixc | |
| ON ixc.object_id = c.object_id | |
| AND ixc.column_id = c.column_id | |
| AND ix.index_id = ixc.index_id | |
| WHERE (t.[name] in (''text'', ''ntext'', ''image'') OR c.is_filestream = 1) | |
| AND ix.object_id = c.object_id | |
| AND (ix.index_id IN (0,1) OR ixc.index_id IS NOT NULL) | |
| ) | |
| GROUP BY | |
| t.object_id | |
| , t.name | |
| , p.index_id | |
| , ix.name' | |
| + CASE WHEN @CheckPerPartition = 1 THEN N', p.partition_number' ELSE '' END | |
| + CASE WHEN ISNULL(@MinimumSizeMB,0) > 0 THEN N' | |
| HAVING | |
| CEILING(SUM(ISNULL(sps.in_row_data_page_count,0) + ISNULL(sps.row_overflow_used_page_count,0) + ISNULL(sps.lob_reserved_page_count,0)) / 128.0) >= ' + CONVERT(nvarchar(MAX), @MinimumSizeMB) | |
| ELSE N'' END + N' | |
| OPTION (RECOMPILE); | |
| SELECT | |
| DB_NAME() | |
| , p.[schema_name] | |
| , p.object_id | |
| , p.table_name | |
| , p.index_id | |
| , p.index_name | |
| , p.partition_number | |
| , p.size_MB | |
| , p.in_row_percent | |
| , range_scans_percent = ISNULL( | |
| FLOOR(SUM(ISNULL(ios.range_scan_count,0)) * 1.0 / | |
| NULLIF(SUM( | |
| ISNULL(ios.range_scan_count,0) + | |
| ISNULL(ios.leaf_delete_count,0) + | |
| ISNULL(ios.leaf_insert_count,0) + | |
| ISNULL(ios.leaf_page_merge_count,0) + | |
| ISNULL(ios.leaf_update_count,0) + | |
| ISNULL(ios.singleton_lookup_count,0) | |
| ), 0) * 100.0), 0) | |
| , updates_percent = ISNULL( | |
| CEILING(SUM(ISNULL(ios.leaf_update_count, 0)) * 1.0 / | |
| NULLIF(SUM( | |
| ISNULL(ios.range_scan_count,0) + | |
| ISNULL(ios.leaf_delete_count,0) + | |
| ISNULL(ios.leaf_insert_count,0) + | |
| ISNULL(ios.leaf_page_merge_count,0) + | |
| ISNULL(ios.leaf_update_count,0) + | |
| ISNULL(ios.singleton_lookup_count,0) | |
| ), 0) * 100.0), 0) | |
| FROM #objects AS p WITH(NOLOCK) | |
| OUTER APPLY sys.dm_db_index_operational_stats(db_id(),p.object_id,p.index_id,p.partition_number) AS ios | |
| GROUP BY | |
| p.object_id | |
| , p.schema_name | |
| , p.table_name | |
| , p.index_id | |
| , p.index_name | |
| , p.partition_number | |
| , p.size_MB | |
| , p.in_row_percent | |
| OPTION (RECOMPILE, MAXDOP 1);' | |
| INSERT INTO @ObjectsToCheck | |
| EXEC sp_executesql @CMD; | |
| /* end of potential for-each-db */ | |
| — Init temp table to hold final results | |
| IF OBJECT_ID('tempdb..#ResultsAll') IS NOT NULL DROP TABLE #ResultsAll; | |
| CREATE TABLE #ResultsAll ( | |
| [database_name] SYSNAME NOT NULL | |
| , [schema_name] SYSNAME NOT NULL | |
| , [table_name] SYSNAME NOT NULL | |
| , [index_name] SYSNAME NULL | |
| , partition_number INT NULL | |
| , size_MB INT NULL | |
| , in_row_percent INT NULL | |
| , scan_percent INT NULL | |
| , update_percent INT NULL | |
| , compression_type VARCHAR(4) NOT NULL | |
| , compression_ratio FLOAT NULL | |
| , compression_size_saving_KB FLOAT NULL | |
| , is_compression_feasible BIT NULL | |
| , is_compression_recommended bit NULL | |
| ) | |
| — Init cursor to traverse all un-compressed tables that were found | |
| DECLARE TablesToCheck CURSOR | |
| LOCAL FORWARD_ONLY FAST_FORWARD | |
| FOR | |
| SELECT | |
| o.[database_name] | |
| , o.[schema_name] | |
| , o.[table_id] | |
| , o.[table_name] | |
| , o.[index_id] | |
| , o.[index_name] | |
| , o.[partition_number] | |
| , ct.CompressionType | |
| , o.size_MB | |
| , o.in_row_percent | |
| , o.range_scans_percent | |
| , o.updates_percent | |
| FROM @ObjectsToCheck AS o | |
| CROSS JOIN (VALUES('PAGE'),('ROW')) AS ct(CompressionType) — check both ROW and PAGE compression for each | |
| OPEN TablesToCheck | |
| FETCH NEXT FROM TablesToCheck | |
| INTO @CurrDB, @Schema, @ObjectId, @Table, @IndexId, @IndexName, @Partition, @CompressionType, @TotalSizeMB, @InRowPercent, @ScanPercent, @UpdatePercent | |
| WHILE @@FETCH_STATUS = 0 | |
| BEGIN | |
| DECLARE @sp_estimate_data_compression_savings NVARCHAR(1000); | |
| SET @sp_estimate_data_compression_savings = QUOTENAME(@CurrDB) + '.sys.sp_estimate_data_compression_savings' | |
| SET @EstimationCheckRecommended = CASE | |
| WHEN @InRowPercent < @MinimumCompressibleDataPercent THEN 0 | |
| WHEN ISNULL(@ScanPercent,0) <= @MinimumScanPctForComparison OR ISNULL(@UpdatePercent,0) <= @MaximumUpdatePctAsInfrequent THEN 1 | |
| WHEN @CompressionType = 'PAGE' AND @ScanPercent >= @MinimumScanPctForPage AND @UpdatePercent <= @MaximumUpdatePctForPage THEN 1 | |
| WHEN @CompressionType = 'ROW' AND @UpdatePercent <= @MaximumUpdatePctForRow THEN 1 | |
| ELSE 0 | |
| END | |
| RAISERROR(N'–Database [%s], table [%s].[%s], index [%s], partition %d: size: %d MB, in-row data: %d percent, range scans: %d percent, updates: %d percent. Compression type: %s',0,1 | |
| ,@CurrDB,@Schema,@Table,@IndexName,@Partition,@TotalSizeMB,@InRowPercent,@ScanPercent,@UpdatePercent,@CompressionType) WITH NOWAIT; | |
| IF @FeasibilityCheckOnly = 0 AND (@MaxSizeMBForActualCheck IS NULL OR (@TotalSizeMB <= @MaxSizeMBForActualCheck AND @TotalSizeMB * 0.05 < @AvailableTempDBSpaceMB)) | |
| BEGIN | |
| IF @EstimationCheckRecommended = 1 | |
| BEGIN | |
| BEGIN TRY | |
| IF @MaximumCPUPercentForRebuild IS NOT NULL | |
| BEGIN | |
| DECLARE @AvgCPU FLOAT, @WaitForCPUStartTime DATETIME; | |
| CpuUtilizationCheck: | |
| SELECT @AvgCPU = AVG( 100 – record.value('(./Record/SchedulerMonitorEvent/SystemHealth/SystemIdle)[1]', 'int') ) | |
| FROM ( | |
| SELECT TOP (@SamplesToCheckAvgForCPUPercent) [timestamp], convert(xml, record) as record | |
| FROM sys.dm_os_ring_buffers | |
| WHERE ring_buffer_type = N'RING_BUFFER_SCHEDULER_MONITOR' | |
| AND record like '%<SystemHealth>%' | |
| ORDER BY [timestamp] DESC | |
| ) as RingBufferInfo | |
| IF @AvgCPU <= @MaximumCPUPercentForRebuild | |
| BEGIN | |
| SET @WaitForCPUStartTime = NULL; | |
| GOTO AfterCpuUtilizationCheck; | |
| END | |
| ELSE IF @MaximumTimeToWaitForCPU IS NOT NULL | |
| BEGIN | |
| IF @WaitForCPUStartTime IS NULL | |
| BEGIN | |
| SET @WaitForCPUStartTime = GETDATE() | |
| END | |
| ELSE IF @WaitForCPUStartTime + @MaximumTimeToWaitForCPU > GETDATE() | |
| BEGIN | |
| RAISERROR(N'— CPU utilization is too high. Aborting check.', 16, 1); | |
| GOTO EndOfCursor; | |
| END | |
| END | |
| WAITFOR DELAY '00:00:00.5' | |
| GOTO CpuUtilizationCheck; | |
| END | |
| AfterCpuUtilizationCheck: | |
| — Calculate compression savings estimation | |
| INSERT INTO @Results | |
| EXEC @sp_estimate_data_compression_savings | |
| @schema_name = @Schema, | |
| @object_name = @Table, | |
| @index_id = @IndexId, | |
| @partition_number = @Partition, | |
| @data_compression = @CompressionType; | |
| END TRY | |
| BEGIN CATCH | |
| DECLARE @EstimationErrMsg NVARCHAR(MAX) | |
| SET @EstimationErrMsg = ERROR_MESSAGE() | |
| RAISERROR(N'— ERROR while running sp_estimate_data_compression_savings: %s',0,1,@EstimationErrMsg); | |
| END CATCH | |
| END | |
| ELSE | |
| BEGIN | |
| RAISERROR(N'— Not a good candidate for compression. Skipping estimation check.',0,1); | |
| SET @ChecksSkipped = 1; | |
| END | |
| END | |
| ELSE IF @FeasibilityCheckOnly = 1 | |
| SET @ChecksSkipped = 1 | |
| ELSE | |
| BEGIN | |
| RAISERROR(N'— Too big for TempDB. Skipping estimation check.',0,1); | |
| SET @ChecksSkipped = 1; | |
| END | |
| — Save to main results table | |
| INSERT INTO #ResultsAll | |
| SELECT | |
| [database_name] = @CurrDB | |
| , [schema_name] = @Schema | |
| , table_name = @Table | |
| , index_name = @IndexName | |
| , partition_number = @Partition | |
| , size_MB = @TotalSizeMB | |
| , in_row_percent = @InRowPercent | |
| , scan_percent = @ScanPercent | |
| , update_percent = @UpdatePercent | |
| , compression_type = @CompressionType | |
| , compression_ratio = 100 – (SUM(ISNULL(r.size_w_requested_compression_KB,0)) * 100.0 / NULLIF(SUM(ISNULL(r.size_w_current_compression_KB,0)),0)) | |
| , compression_size_saving_KB = SUM(ISNULL(r.size_w_current_compression_KB,0)) – SUM(ISNULL(r.size_w_requested_compression_KB,0)) | |
| , is_compression_feasible = @EstimationCheckRecommended | |
| , is_compression_recommended = CASE | |
| WHEN @FeasibilityCheckOnly = 1 OR @EstimationCheckRecommended = 0 THEN NULL | |
| WHEN | |
| 100 – (SUM(ISNULL(r.size_w_requested_compression_KB,0)) * 100.0 / NULLIF(SUM(ISNULL(r.size_w_current_compression_KB,0)),0)) >= @CompressionRatioThreshold | |
| AND (SUM(ISNULL(r.size_w_current_compression_KB,0)) – SUM(ISNULL(r.size_w_requested_compression_KB,0))) / 1024.0 >= @CompressionSizeSavedMBThreshold | |
| THEN 1 | |
| ELSE 0 END | |
| FROM | |
| @Results AS r | |
| OPTION (RECOMPILE); | |
| DELETE @Results; | |
| FETCH NEXT FROM TablesToCheck | |
| INTO @CurrDB, @Schema, @ObjectId, @Table, @IndexId, @IndexName, @Partition, @CompressionType, @TotalSizeMB, @InRowPercent, @ScanPercent, @UpdatePercent | |
| END | |
| EndOfCursor: | |
| CLOSE TablesToCheck | |
| DEALLOCATE TablesToCheck | |
| IF @ChecksSkipped = 1 | |
| BEGIN | |
| PRINT N'— One or more tables were not checked. Please adjust threshold parameter values and make sure you have enough free disk space if you want to run those checks anyway.' | |
| END | |
| — Return results to client | |
| SELECT | |
| [database_name] | |
| ,[schema_name] | |
| ,[table_name] | |
| ,full_table_name = QUOTENAME([schema_name]) + '.' + QUOTENAME([table_name]) | |
| ,index_name | |
| ,partition_number = ISNULL(CONVERT(varchar(256),partition_number),'ALL') | |
| ,size_MB | |
| ,compressible_data = CONVERT(varchar(10), in_row_percent) + ' %' | |
| ,scan_percent = CONVERT(varchar(10), scan_percent) + ' %' | |
| ,update_percent = CONVERT(varchar(10), update_percent) + ' %' | |
| ,compression_type | |
| ,compression_ratio = ROUND(compression_ratio,3) | |
| ,compression_size_saving_MB = compression_size_saving_KB / 1024.0 | |
| ,is_compression_candidate = CASE WHEN is_compression_feasible = 1 THEN 'Yes' ELSE 'No' END | |
| ,is_compression_recommended = CASE | |
| WHEN is_compression_recommended IS NULL AND is_compression_feasible = 1 THEN | |
| CASE | |
| WHEN in_row_percent < @MinimumCompressibleDataPercent THEN N'No' | |
| WHEN compression_type = 'PAGE' AND ISNULL(scan_percent,0) <= @MinimumScanPctForComparison AND ISNULL(update_percent,0) <= @MaximumUpdatePctAsInfrequent THEN 'Yes' | |
| WHEN scan_percent >= @MinimumScanPctForPage AND update_percent <= @MaximumUpdatePctForPage THEN | |
| CASE WHEN compression_type = 'PAGE' THEN 'Yes' ELSE 'No' END | |
| WHEN update_percent <= @MaximumUpdatePctForRow THEN | |
| CASE WHEN compression_type = 'ROW' THEN 'Yes' ELSE 'No' END | |
| ELSE 'No' | |
| END + ' (best guess)' | |
| WHEN is_compression_recommended = 1 AND SavingsRating = 1 THEN 'Yes' ELSE 'No' | |
| END | |
| ,remediation_command = | |
| CASE WHEN ISNULL(is_compression_recommended,0) = 0 OR SavingsRating <> 1 THEN N'— ' ELSE N'' END | |
| + N'USE ' + QUOTENAME([database_name]) + N'; ALTER ' + ISNULL(N'INDEX ' + QUOTENAME(index_name) + N' ON ', N'TABLE ') + QUOTENAME([schema_name]) + '.' + QUOTENAME([table_name]) | |
| + N' REBUILD PARTITION = ' + ISNULL(CONVERT(nvarchar(max),partition_number), N'ALL') | |
| + N' WITH (DATA_COMPRESSION = ' + compression_type + @RebuildOptions + N');' | |
| FROM | |
| ( | |
| SELECT | |
| *, SavingsRating = ROW_NUMBER() OVER ( | |
| PARTITION BY | |
| [database_name] | |
| , table_name | |
| , index_name | |
| , partition_number | |
| , is_compression_recommended | |
| ORDER BY | |
| compression_ratio + (CASE WHEN compression_type = 'ROW' THEN @MinimumRatioDifferenceForPage ELSE 0 END) DESC, | |
| compression_size_saving_KB + (CASE WHEN compression_type = 'ROW' THEN ISNULL(@MinimumSavingsMBDifferenceForPage,0) * 1024.0 ELSE 0 END) DESC | |
| ) | |
| FROM #ResultsAll | |
| ) AS r | |
| ORDER BY | |
| [database_name] ASC | |
| , compression_size_saving_KB DESC | |
| , compression_ratio DESC | |
| , size_MB DESC | |
| OPTION (RECOMPILE); | |
| IF @@ROWCOUNT > 0 AND @FeasibilityCheckOnly = 0 | |
| BEGIN | |
| — Begin generating remediation script that takes into consideration all checks | |
| — including ROW vs. PAGE considerations | |
| DECLARE @PrevDB SYSNAME; | |
| SET @PrevDB = N''; | |
| SET @CMD = NULL; | |
| PRINT N'———————————————————————–' | |
| PRINT N'———- Recommendation Script Begins Below ————————-' | |
| PRINT N'———————————————————————–' | |
| DECLARE Rebuilds CURSOR | |
| LOCAL FORWARD_ONLY FAST_FORWARD | |
| FOR | |
| SELECT | |
| [database_name] | |
| , InsertCmd = N'INSERT INTO #INDEXTABLE VALUES (' | |
| + ISNULL(QUOTENAME([index_name], N''''), N'NULL') + N', ' | |
| + QUOTENAME(QUOTENAME([schema_name]) + N'.' + QUOTENAME([table_name]), N'''') + N', ' | |
| + ISNULL(CONVERT(nvarchar(max), partition_number), N'NULL') + N', ' | |
| + QUOTENAME([compression_type], N'''') + N');' | |
| —, RemediationCmd = N'USE ' + QUOTENAME([database_name]) + N'; ALTER ' + ISNULL(N'INDEX ' + QUOTENAME(index_name) + N' ON ', N'TABLE ') + QUOTENAME([schema_name]) + '.' + QUOTENAME([table_name]) + N' | |
| —REBUILD PARTITION = ' + ISNULL(CONVERT(nvarchar,partition_number), N'ALL') + N' WITH (DATA_COMPRESSION = ' + compression_type + @RebuildOptions + N');' | |
| —, StatusMessage = QUOTENAME([database_name]) + N': ' + ISNULL(N'INDEX ' + QUOTENAME(index_name) + N' ON ', N'TABLE ') + QUOTENAME([schema_name]) + N'.' + QUOTENAME([table_name]) | |
| — + N' PARTITION = ' + ISNULL(CONVERT(nvarchar,partition_number), N'ALL') + N', DATA_COMPRESSION = ' + compression_type | |
| FROM | |
| ( | |
| SELECT | |
| [database_name] | |
| , [schema_name] | |
| , table_name | |
| , index_name | |
| , compression_size_saving_KB | |
| , compression_ratio | |
| , compression_type | |
| , partition_number | |
| , SavingsRating = ROW_NUMBER() OVER ( | |
| PARTITION BY | |
| [database_name] | |
| , table_name | |
| , index_name | |
| , partition_number | |
| ORDER BY | |
| compression_ratio + (CASE WHEN compression_type = 'ROW' THEN @MinimumRatioDifferenceForPage ELSE 0 END) DESC, | |
| compression_size_saving_KB + (CASE WHEN compression_type = 'ROW' THEN ISNULL(@MinimumSavingsMBDifferenceForPage,0) * 1024.0 ELSE 0 END) DESC | |
| ) | |
| FROM | |
| #ResultsAll | |
| WHERE | |
| is_compression_recommended = 1 | |
| ) AS q | |
| WHERE SavingsRating = 1 | |
| ORDER BY | |
| [database_name] ASC | |
| , compression_size_saving_KB DESC | |
| , compression_ratio DESC | |
| OPEN Rebuilds | |
| FETCH NEXT FROM Rebuilds INTO @CurrDB, @CMD | |
| WHILE @@FETCH_STATUS = 0 | |
| BEGIN | |
| IF @CurrDB <> @PrevDB | |
| BEGIN | |
| PRINT N'USE ' + QUOTENAME(@CurrDB) + N'; | |
| DECLARE @Size INT, @DB SYSNAME; | |
| SELECT @Size = SUM(FILEPROPERTY([name], ''SpaceUsed'')) / 128.0 FROM sys.database_files WHERE type = 0; | |
| SET @DB = DB_NAME(); | |
| RAISERROR(N''Space used for data in "%s" BEFORE compression: %d MB'', 0, 1, @DB, @Size) WITH NOWAIT; | |
| GO | |
| SET NOCOUNT, QUOTED_IDENTIFIER, ARITHABORT, XACT_ABORT ON; | |
| IF OBJECT_ID(''tempdb..#INDEXTABLE'') IS NOT NULL DROP TABLE #INDEXTABLE; | |
| CREATE TABLE #INDEXTABLE ( | |
| IndexName SYSNAME NULL, | |
| TableName NVARCHAR(4000) NOT NULL, | |
| PartitionNumber INT NULL, | |
| CompressionType SYSNAME NOT NULL | |
| ) | |
| ' | |
| SET @PrevDB = @CurrDB; | |
| END | |
| PRINT @CMD; | |
| FETCH NEXT FROM Rebuilds INTO @CurrDB, @CMD; | |
| IF @@FETCH_STATUS <> 0 OR @CurrDB <> @PrevDB | |
| BEGIN | |
| PRINT N'GO | |
| USE ' + QUOTENAME(@PrevDB) + N'; | |
| DECLARE @WhatIf BIT = 0 | |
| SET NOCOUNT, QUOTED_IDENTIFIER, ARITHABORT, XACT_ABORT ON; | |
| DECLARE @DB SYSNAME; | |
| SET @DB = DB_NAME(); | |
| DECLARE @time VARCHAR(25) | |
| DECLARE @IndexName SYSNAME, @TableName NVARCHAR(4000), @PartitionNumber INT, @CompressionType SYSNAME, @CMD NVARCHAR(MAX)' | |
| PRINT N'DECLARE TablesToCheck CURSOR | |
| LOCAL FORWARD_ONLY FAST_FORWARD | |
| FOR | |
| SELECT IndexName, TableName, PartitionNumber, CompressionType, | |
| Cmd = N''USE '' + QUOTENAME(@DB) + N''; ALTER '' + ISNULL(N''INDEX '' + QUOTENAME(IndexName) + N'' ON '', N''TABLE '') + TableName | |
| + N'' REBUILD PARTITION = '' + ISNULL(CONVERT(nvarchar,PartitionNumber), N''ALL'') | |
| + N'' WITH (DATA_COMPRESSION = '' + CompressionType + N''' + @RebuildOptions + N');'' | |
| FROM #INDEXTABLE | |
| OPEN TablesToCheck | |
| WHILE 1 = 1 | |
| BEGIN | |
| FETCH NEXT FROM TablesToCheck INTO @IndexName, @TableName, @PartitionNumber, @CompressionType, @CMD | |
| IF @@FETCH_STATUS <> 0 | |
| BREAK;' | |
| IF @AllowedRuntimeHourFrom IS NOT NULL AND @AllowedRuntimeHourTo IS NOT NULL | |
| PRINT N' | |
| IF DATEPART(hour, GETDATE()) NOT BETWEEN ' + CONVERT(nvarchar(MAX), @AllowedRuntimeHourFrom) + N' AND ' + CONVERT(nvarchar(MAX), @AllowedRuntimeHourTo) + N' | |
| BEGIN | |
| SET @time = CONVERT(VARCHAR(25), GETDATE(), 121); | |
| RAISERROR(N''%s – Reached outside allowed execution time.'', 0, 1, @time); | |
| BREAK; | |
| END' | |
| IF @NotAllowedRuntimeHourFrom IS NOT NULL AND @NotAllowedRuntimeHourTo IS NOT NULL | |
| PRINT N' | |
| IF DATEPART(hour, GETDATE()) BETWEEN ' + CONVERT(nvarchar(MAX), @NotAllowedRuntimeHourFrom) + N' AND ' + CONVERT(nvarchar(MAX), @NotAllowedRuntimeHourTo) + N' | |
| BEGIN | |
| SET @time = CONVERT(VARCHAR(25), GETDATE(), 121); | |
| RAISERROR(N''%s – Reached outside allowed execution time.'', 0, 1, @time); | |
| BREAK; | |
| END' | |
| IF @MaximumCPUPercentForRebuild IS NOT NULL | |
| PRINT N' | |
| DECLARE @AvgCPU FLOAT, @WaitForCPUStartTime DATETIME; | |
| CpuUtilizationCheck: | |
| SELECT @AvgCPU = AVG( 100 – record.value(''(./Record/SchedulerMonitorEvent/SystemHealth/SystemIdle)[1]'', ''int'') ) | |
| from ( | |
| SELECT TOP (' + CONVERT(nvarchar(MAX), @SamplesToCheckAvgForCPUPercent) + N') [timestamp], convert(xml, record) as record | |
| FROM sys.dm_os_ring_buffers | |
| WHERE ring_buffer_type = N''RING_BUFFER_SCHEDULER_MONITOR'' | |
| AND record like ''%<SystemHealth>%'' | |
| ORDER BY [timestamp] DESC | |
| ) as RingBufferInfo | |
| IF @AvgCPU <= ' + CONVERT(nvarchar(MAX), @MaximumCPUPercentForRebuild) + N' | |
| BEGIN | |
| SET @WaitForCPUStartTime = NULL; | |
| END' + CASE WHEN @MaximumTimeToWaitForCPU IS NOT NULL THEN N' | |
| ELSE IF @WaitForCPUStartTime IS NULL | |
| BEGIN | |
| SET @WaitForCPUStartTime = GETDATE() | |
| GOTO CpuUtilizationCheck; | |
| END | |
| ELSE IF @WaitForCPUStartTime + ' + QUOTENAME(CONVERT(nvarchar(max), @MaximumTimeToWaitForCPU, 121), N'''') + N' > GETDATE() | |
| BEGIN | |
| SET @time = CONVERT(VARCHAR(25), GETDATE(), 121); | |
| RAISERROR(N''%s – CPU utilization is too high.'', 0, 1, @time); | |
| BREAK; | |
| END' ELSE N'' END + N' | |
| ELSE | |
| BEGIN | |
| WAITFOR DELAY ''00:00:00.5'' | |
| GOTO CpuUtilizationCheck; | |
| END' | |
| PRINT N' | |
| — Check if index has no compression | |
| IF EXISTS ( | |
| SELECT NULL | |
| FROM sys.partitions AS p WITH (NOLOCK) | |
| INNER JOIN sys.indexes AS ix WITH (NOLOCK) | |
| ON ix.object_id = p.object_id | |
| AND ix.index_id = p.index_id | |
| WHERE ix.object_id = OBJECT_ID(@TableName) | |
| AND (ix.name = @IndexName OR (@IndexName IS NULL AND ix.index_id = 0)) | |
| AND p.data_compression_desc <> @CompressionType | |
| AND (@PartitionNumber IS NULL OR p.partition_number = @PartitionNumber) | |
| ) | |
| BEGIN | |
| SET @time = CONVERT(VARCHAR(25), GETDATE(), 121); | |
| RAISERROR (N''%s – [%s]: INDEX [%s] ON %s PARTITION = %s, DATA_COMPRESSION = %s'', 0, 1, @time, @DB, @IndexName, @TableName, @PartitionNumber, @CompressionType) WITH NOWAIT; | |
| PRINT @CMD; | |
| IF @WhatIf = 0 EXEC sp_executesql @CMD; | |
| END | |
| END | |
| CLOSE TablesToCheck | |
| DEALLOCATE TablesToCheck | |
| DROP TABLE #INDEXTABLE | |
| GO' | |
| PRINT N'USE ' + QUOTENAME(@PrevDB) + N'; | |
| DECLARE @Size INT, @DB SYSNAME; | |
| SET @DB = DB_NAME(); | |
| SELECT @Size = SUM(FILEPROPERTY([name], ''SpaceUsed'')) / 128.0 FROM sys.database_files WHERE type = 0; | |
| RAISERROR(N''Space used for data in "%s" AFTER compression: %d MB'', 0, 1, @DB, @Size) WITH NOWAIT; | |
| GO' | |
| END —IF @@FETCH_STATUS <> 0 OR @CurrDB <> @PrevDB | |
| END — WHILE @@FETCH_STATUS = 0 | |
| PRINT N'DECLARE @time VARCHAR(25) = CONVERT(varchar(25), GETDATE(), 121); RAISERROR(N''%s – Done'',0,1,@time) WITH NOWAIT;' | |
| CLOSE Rebuilds | |
| DEALLOCATE Rebuilds | |
| PRINT N'———————————————————————–' | |
| PRINT N'———– Recommendation Script Ends Here ————————–' | |
| PRINT N'———————————————————————–' | |
| END | |
| ELSE IF @FeasibilityCheckOnly = 1 | |
| BEGIN | |
| PRINT N'———————————————————————–' | |
| PRINT N'——– Feasibility Check Only – No Script Generated —————–' | |
| PRINT N'———————————————————————–' | |
| END | |
| ELSE | |
| BEGIN | |
| PRINT N'———————————————————————–' | |
| PRINT N'———– No Candidates for Compression Found ———————–' | |
| PRINT N'———————————————————————–' | |
| END | |
| PRINT N'GO' | |
| Quit: |
The script is also mirror-published at Madeira’s Toolbox GitHub repository here.
License and Disclaimer
The script is completely free and is provided as-is, without any warrantee. Use at your own risk, and as stated above, be extra careful when running it in production environments.
Possible side-effects may include (especially if executed within very large databases):
- Extra IO workload
- Extra CPU workload
- Extra schema-level locks
- Extra disk-space used by TempDB
- Rapid loss of disk free space
- Possible schema-level deadlocks (in some SQL versions. It may be solved using MAXDOP 1 at instance-level)
- Extra time spent in front of your computer while sweating profusely
- … or extra requirement of coffee intake
- … or booze
- … or a sudden inexplicable need to seek new job openings
- … or all of the above!
Please handle with care! 😉
Additional Resources
If this topic interests you, you should check out the following resources which may give you additional perspective on compression savings estimation in SQL server. I used these resources myself while building this script:
- What_to_Compress_v2 by SQLBalls at SQLServerCentral.com
- Estimate compression for all tables and indexes with both Row and Page by DawnLove at SQLServerCentral.com
- Compression Estimates by osragde at SQLServerCentral.com
- Evaluation Compression Gains by Microsoft Tiger Team
- Data compression in SQL Server (Microsoft Docs)
Enjoy!
Cover Image by Gerd Altmann from Pixabay
[…] Maybe you deleted or migrated a huge chunk of data which you know will never return. Maybe you activated data compression on a significant portion of your tables and now you want to reclaim that freed space for other uses. Or maybe you simply have a very […]
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[…] Regardless of this disappointment, data compression in SQL Server is still awesome with a bunch of other benefits and you should definitely use it. […]
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[…] This script is a simplified version of a remediation script generated by my ultimate compression savings estimation script. […]
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Have you considered adding Columnstore compression?
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Yes, actually. I did indeed. However, considerations for columnstore indexing are exceedingly more complex than what can be inferred from the SQL server metadata.
There are other similar solutions out there specifically dedicated for columnstore index considerations.
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Here is an example:
https://columnscore.com/
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