Truncate table updating statistics

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The thresholds for when auto-update statistics kicks in are a little complicated.For SQL Server 2005 – SQL Server 2014 (with no trace flags) to make an optimization decision that the update is kicked off. Trace Flag 2371 makes the formula for large tables more dynamic.If it looks like a significant amount of rows in the column have changed, SQL Server updates the statistic, then optimizes the query.

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Prior to 2016, here’s a quick rundown of pros and cons of TF2371: Overall, this is a low risk trace flag.

But in general it does NOT pay off to enable trace flags “just in case” for most people.

First Name By Year') and s.auto_created = 1 ORDER BY sc.stats_column_id; GO Sure enough, here are our statistics, and they are on Gender and First Name Id.

These are not considered ‘user created’ even though our user query was the cause of them being auto-generated.

If you have multiple SQL Servers using shared storage, that maintenance may hit the storage at the same time. ⇒ The moderate approach: One widely used free script is Ola Hallengren’s SQL Server Index and Statistics Maintenance script.

If you’re managing lots of SQL Server instances and want ultimate customization, there is a free version of Minion Reindex. The answers to both of these questions impact what it does to GROUP those rows and SUM the Name Count column.Statistics take up a negligible amount of space compared to indexes.With default database settings, the SQL Server optimizer looks at how many changes have occurred for a given column statistic as part of query optimization.Auto-created statistics are incredibly small, and you only get one per column in a table.Even if you have a statistic on every column in the table, this is a very small amount of overhead.Just truncate the table and verify what happens with NUM_ROWS (or any other statistics related columns) in USER_TABLES for that table. select * from user_tables where table_name = 'TEST'; TABLE_NAME TABLESPACE_NAME ------------------------------ ------------------------------ CLUSTER_NAME IOT_NAME PCT_FREE ------------------------------ ------------------------------ ---------- PCT_USED INI_TRANS MAX_TRANS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS ---------- ---------- ---------- -------------- ----------- ----------- MAX_EXTENTS PCT_INCREASE FREELISTS FREELIST_GROUPS LOG B NUM_ROWS BLOCKS ----------- ------------ ---------- --------------- --- - ---------- ---------- EMPTY_BLOCKS AVG_SPACE CHAIN_CNT AVG_ROW_LEN AVG_SPACE_FREELIST_BLOCKS ------------ ---------- ---------- ----------- ------------------------- NUM_FREELIST_BLOCKS DEGREE INSTANCES CACHE TABLE_LO SAMPLE_SIZE LAST_ANAL ------------------- ---------- ---------- ----- -------- ----------- --------- PAR IOT_TYPE T S NES BUFFER_ ROW_MOVE GLO USE DURATION SKIP_COR MON --- ------------ - - --- ------- -------- --- --- --------------- -------- --- CLUSTER_OWNER DEPENDEN ------------------------------ -------- TEST USERS 10 576 1 2147483645 YES N 1 61 3 16265 0 6 0 0 1 1 N ENABLED 1 27-SEP-02 NO N N NO DEFAULT DISABLED NO NO DISABLED NO DISABLED SQL select * from user_tables where table_name = 'TEST'; TABLE_NAME TABLESPACE_NAME ------------------------------ ------------------------------ CLUSTER_NAME IOT_NAME PCT_FREE ------------------------------ ------------------------------ ---------- PCT_USED INI_TRANS MAX_TRANS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS ---------- ---------- ---------- -------------- ----------- ----------- MAX_EXTENTS PCT_INCREASE FREELISTS FREELIST_GROUPS LOG B NUM_ROWS BLOCKS ----------- ------------ ---------- --------------- --- - ---------- ---------- EMPTY_BLOCKS AVG_SPACE CHAIN_CNT AVG_ROW_LEN AVG_SPACE_FREELIST_BLOCKS ------------ ---------- ---------- ----------- ------------------------- NUM_FREELIST_BLOCKS DEGREE INSTANCES CACHE TABLE_LO SAMPLE_SIZE LAST_ANAL ------------------- ---------- ---------- ----- -------- ----------- --------- PAR IOT_TYPE T S NES BUFFER_ ROW_MOVE GLO USE DURATION SKIP_COR MON --- ------------ - - --- ------- -------- --- --- --------------- -------- --- CLUSTER_OWNER DEPENDEN ------------------------------ -------- TEST USERS 10 576 1 2147483645 YES N 1 61 3 16265 0 6 0 0 1 1 N ENABLED 1 27-SEP-02 NO N N NO DEFAULT DISABLED NO NO DISABLED NO DISABLED And there you go...I’ve been asked a lot of questions about updating statistics in SQL Server over the years. Here’s a rundown of all the practical questions that I tend to get about how to maintain these in SQL Server.Statistics are small, lightweight objects that describe the distribution of data in a SQL Server table. First Name By Year and you run this query: SQL Server needs to estimate how many rows will come back for First Name Id=74846. Statistics are lightweight little pieces of information that SQL Server keeps on tables and indexes to help the optimizer do a good job. First Name By Year table was freshly created when we ran our query, it would have no column statistics.The SQL Server query optimizer uses statistics to estimate how many rows will be returned by parts of your query. By default, the SQL Server optimizer will see that no statistics exists, and wait while two column statistics are created on the First Name Id and Gender columns.(That is pretty much limited to weirdoes like Share Point.) In rare situations, manually creating a multi-column statistic or a filtered statistic can improve performance…but keep reading to find out what those are and why it’s rare to require them.

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Comments Truncate table updating statistics

  • Updating InnoDB Table Statistics
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    InnoDB stores statistics in the “mysql” database, in the tables innodb_table_stats and innodb_index_stats. Since they are regular MySQL tables, privileged users can access…

  • Truncate Command and Table
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    Statistics looks good in USER_TABLES. Now let's try to TRUNCATE the table and see what happens to Statistics. [email protected] TRUNCATE TABLE EMP; Table truncated.…

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    Use the TRUNCATE statement to quickly delete all rows from a local table and free the associated storage space. You can optionally reserve the space for.…

  • Truncate Table and Statistics in 2005 -
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    If you are deleting ALL the data from the table who cares about the statistics. They will be meaningless until new data is inserted and the stats get updated.…

  • How to UPDATE STATISTICS in SQL
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    I am trying to UPDATE STATISTICS for a table in a database and when I do so and verify the count of. -- Truncate the Table TRUNCATE.…

  • Updating Statistics in SQL Server
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    If you run UPDATE STATISTICS against a table. Updating Statistics in SQL Server. Does Truncate Table Reset Statistics.…

  • Truncate table - are the stats gone? -
    Reply

    Why don't you try it for yourself, it is trivial to test it. Just truncate the table and verify what happens with NUM_ROWS or any other statistics related.…

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