Skip to content

sp_BlitzIndex: Added warning for persisted sample rates. #3680

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: dev
Choose a base branch
from
+36 −10
Open

sp_BlitzIndex: Added warning for persisted sample rates. #3680

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 3 additions & 2 deletions Documentation/sp_BlitzIndex_Checks_by_Priority.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,8 @@ Before adding a new check, make sure to add a Github issue for it first, and hav

If you want to change anything about a check - the priority, finding, URL, or ID - open a Github issue first. The relevant scripts have to be updated too.

CURRENT HIGH CHECKID: 124
If you want to add a new check, start at 125.
CURRENT HIGH CHECKID: 125
If you want to add a new check, start at 126.

| Priority | FindingsGroup | Finding | URL | CheckID |
| -------- | ----------------------- | --------------------------------------------------------------- | ---------------------------------------------------------------- | ------- |
Expand All @@ -25,6 +25,7 @@ If you want to add a new check, start at 125.
| 80 | Abnormal Design Pattern | Filter Columns Not In Index Definition | https://www.brentozar.com/go/IndexFeatures | 34 |
| 80 | Abnormal Design Pattern | History Table With NonClustered Index | https://sqlserverfast.com/blog/hugo/2023/09/an-update-on-merge/ | 124 |
| 90 | Statistics Warnings | Low Sampling Rates | https://www.brentozar.com/go/stats | 91 |
| 90 | Statistics Warnings | Persisted Sampling Rates | https://www.youtube.com/watch?v=V5illj_KOJg&t=758s | 125 |
| 90 | Statistics Warnings | Statistics Not Updated Recently | https://www.brentozar.com/go/stats | 90 |
| 90 | Statistics Warnings | Statistics with NO RECOMPUTE | https://www.brentozar.com/go/stats | 92 |
| 100 | Over-Indexing | NC index with High Writes:Reads | https://www.brentozar.com/go/IndexHoarder | 48 |
Expand Down
41 changes: 33 additions & 8 deletions sp_BlitzIndex.sql
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -738,7 +738,8 @@ IF OBJECT_ID('tempdb..#dm_db_index_operational_stats') IS NOT NULL
table_modify_date DATETIME NULL,
no_recompute BIT NULL,
has_filter BIT NULL,
filter_definition NVARCHAR(MAX) NULL
filter_definition NVARCHAR(MAX) NULL,
has_persisted_sample BIT NULL
);

CREATE TABLE #ComputedColumns
Expand Down Expand Up @@ -2279,7 +2280,7 @@ OPTION (RECOMPILE);';
INSERT #Statistics ( database_id, database_name, table_name, schema_name, index_name, column_names, statistics_name, last_statistics_update,
days_since_last_stats_update, rows, rows_sampled, percent_sampled, histogram_steps, modification_counter,
percent_modifications, modifications_before_auto_update, index_type_desc, table_create_date, table_modify_date,
no_recompute, has_filter, filter_definition)
no_recompute, has_filter, filter_definition, has_persisted_sample)
SELECT DB_ID(N' + QUOTENAME(@DatabaseName,'''') + N') AS [database_id],
@i_DatabaseName AS database_name,
obj.name AS table_name,
Expand All @@ -2306,7 +2307,12 @@ OPTION (RECOMPILE);';
CONVERT(DATETIME, obj.modify_date) AS table_modify_date,
s.no_recompute,
s.has_filter,
s.filter_definition
s.filter_definition,
'
+ CASE WHEN (PARSENAME(@SQLServerProductVersion, 4) >= 15)
THEN N's.has_persisted_sample'
ELSE N'NULL AS has_persisted_sample' END
+ N'
FROM ' + QUOTENAME(@DatabaseName) + N'.sys.stats AS s
JOIN ' + QUOTENAME(@DatabaseName) + N'.sys.objects obj
ON s.object_id = obj.object_id
Expand Down Expand Up @@ -2354,7 +2360,7 @@ OPTION (RECOMPILE);';
INSERT #Statistics(database_id, database_name, table_name, schema_name, index_name, column_names, statistics_name,
last_statistics_update, days_since_last_stats_update, rows, modification_counter,
percent_modifications, modifications_before_auto_update, index_type_desc, table_create_date, table_modify_date,
no_recompute, has_filter, filter_definition)
no_recompute, has_filter, filter_definition, has_persisted_sample)
SELECT DB_ID(N' + QUOTENAME(@DatabaseName,'''') + N') AS [database_id],
@i_DatabaseName AS database_name,
obj.name AS table_name,
Expand All @@ -2379,9 +2385,11 @@ OPTION (RECOMPILE);';
'
+ CASE WHEN @SQLServerProductVersion NOT LIKE '9%'
THEN N's.has_filter,
s.filter_definition'
s.filter_definition,'
ELSE N'NULL AS has_filter,
NULL AS filter_definition' END
NULL AS filter_definition,' END
/* If we are on this branch, then we cannot have the has_persisted_sample column (it is a 2019+ column). */
+ N'NULL AS has_persisted_sample'
+ N'
FROM ' + QUOTENAME(@DatabaseName) + N'.sys.stats AS s
INNER HASH JOIN ' + QUOTENAME(@DatabaseName) + N'.sys.sysindexes si
Expand Down Expand Up @@ -4454,7 +4462,7 @@ BEGIN
END;

----------------------------------------
--Statistics Info: Check_id 90-99
--Statistics Info: Check_id 90-99, as well as 125
----------------------------------------

RAISERROR(N'check_id 90: Outdated statistics', 0,1) WITH NOWAIT;
Expand Down Expand Up @@ -4503,6 +4511,24 @@ BEGIN
OR (s.rows > 1000000 AND s.percent_sampled < 1)
OPTION ( RECOMPILE );

RAISERROR(N'check_id 125: Statistics with a persisted sample rate', 0,1) WITH NOWAIT;
INSERT #BlitzIndexResults ( check_id, Priority, findings_group, finding, [database_name], URL, details, index_definition,
secret_columns, index_usage_summary, index_size_summary )
SELECT 125 AS check_id,
90 AS Priority,
'Statistics Warnings' AS findings_group,
'Persisted Sampling Rates',
s.database_name,
'https://www.youtube.com/watch?v=V5illj_KOJg&t=758s' AS URL,
'The statistics sample rate/amount has been persisted here. ' + CONVERT(NVARCHAR(100), s.percent_sampled) + '% of the rows were sampled during the last statistics update. This may indicate that somebody is doing statistics rocket surgery. Perhaps you would be better off updating statistics more frequently?' AS details,
QUOTENAME(database_name) + '.' + QUOTENAME(s.schema_name) + '.' + QUOTENAME(s.table_name) + '.' + QUOTENAME(s.index_name) + '.' + QUOTENAME(s.statistics_name) + '.' + QUOTENAME(s.column_names) AS index_definition,
'N/A' AS secret_columns,
'N/A' AS index_usage_summary,
'N/A' AS index_size_summary
FROM #Statistics AS s
WHERE s.has_persisted_sample = 1
OPTION ( RECOMPILE );

RAISERROR(N'check_id 92: Statistics with NO RECOMPUTE', 0,1) WITH NOWAIT;
INSERT #BlitzIndexResults ( check_id, Priority, findings_group, finding, [database_name], URL, details, index_definition,
secret_columns, index_usage_summary, index_size_summary )
Expand All @@ -4521,7 +4547,6 @@ BEGIN
WHERE s.no_recompute = 1
OPTION ( RECOMPILE );


RAISERROR(N'check_id 94: Check Constraints That Reference Functions', 0,1) WITH NOWAIT;
INSERT #BlitzIndexResults ( check_id, Priority, findings_group, finding, [database_name], URL, details, index_definition,
secret_columns, index_usage_summary, index_size_summary )
Expand Down
Loading