sql tuning advisor

Tags: process optimizer consolidation requires merging auto overwrite session accessThe full execution order of the SELECT statement:The full execution order of the SQL SELECT statement: 1. The FROM clause assembles data from different data sources; 2. The WHERE clause filters the record rows based on the specified criteria, 3, the GROUP BY clause divides the data into multiple groupings, 4, uses the aggregation function for the calculation, 5, uses t

calculation.In fact, the goal of bitmap computing is very simple: pre-filtering , because our statement requires the result item to compare more than 10000 rows of data, in the thread behind us to take the parallel scan of the way to obtain the data. Due to the large amount of data, the various threads in the process of the completion of data acquisition time is different, in order to avoid the slow execution of a thread, resulting in overall congestion, the index introduced a bitmap operation

be sorted, or it can be added to a column (like joins or additions). Any non-indexed item in the ORDER BY statement, or a computed expression, will slow down the query. Double-check the order BY statement to find non-indexed items or expressions that degrade performance. The solution to this problem is to rewrite the order BY statement to use the index, or you can establish another index for the column you are using, and you should absolutely avoid using an expression in the ORDER BY clause.(a)

released, the data page will not be in the memory of the data cache, This causes the memory problem to be the bottleneck of the disk. PAGEIOLATCH_EX is write data, this is generally the disk write speed obviously keep up, and memory is not directly related. Here is the resource wait time for query pageiolatch_x: Select Wait_type, waiting_tasks_count, Wait_time_ms, Max_wait_time_ms, Signal_wait_time_ms from sys.dm_os_wait_stats wherelike' pageiolatch%' order by Wait_type Through the above

Label:1. Pure hand-crafted Tools: Programmer's hands Features: Handwritten client and server-side validation code 2. Semi-manual semi-automatic Tools: Jquery.validate (client) + dataannotations dataannotationsextensions (server side) Features: Client handwritten partial validation code, server side only need to declare validation rules 3. Fully Automatic Tools: Jquery.validate jquery.validate.unobtrusive (client) + dataannotations dataannotationsextensions (server side) Features: Only server-

union and UnionAll. UnionAll Good 18, pay attention to using distinct, do not use when not necessary, it will make the query slower than the union. Duplicate records are not a problem in the query. 19. Do not return rows or columns that are not required when querying 20. Use sp_configure ' query governor cost limit ' or setquery_governor_cost_limit to limit the resources consumed by the query. When an estimate query consumes more resources than the limit, the server automatically cancels the qu

time and reduce the syntax errors caused by the column ambiguity. 14. Replace distinct with exists:When submitting a query that contains one-to-many table information, avoid using DISTINCT in the SELECT clause. You can generally consider replacing with exists Example: (Low efficiency) Select from where d.dept_no = e.dept_no; Efficient Select from where exists (select1fromwhere d.dept_no = e.dept_no); exists makes queries faster because the RDBMS core module returns results immediately after t

After setting the SET statistics profile, you will return to the Execution plan table, through which you can understand the process of statement execution and understand if SQL Server chooses the correct execution plan to determine the tuning direction!1. Returns the table field description:Rows: The actual number of rows returned in each step of the execution planExecutes: number of executions per step of

SQL Server database self-optimizing release time under large data volume:2013-12-17 15:19:00 Source: Forum anonymous Keywords: database development1.1: Add secondary data filesStarting with SQL SERVER 2005, the database does not generate the NDF data file by default, generally there is a master data file (MDF) is enough, but some large databases, because of a lot of information, and query frequently, so in

Label:Original address: Http://social.technet.microsoft.com/wiki/contents/articles/4995.sql-server-columnstore-performance-tuning.aspxSQL Server's Columnstore index is a new version of SQL Server release that improves query performance for the Data Warehouse, and this article explains the performance tuning of Columnstore.　　Basic principles of Columnstore Index p

index, the TPS from the previous 110 to 6000 such. Two. The SQL statement index does not work: When performing a performance test, the server is running under the circumstances: The CPU of the database is up to 90%-99.9%, and the CPU of the application is low; Sufficient memory (free memory >20m); Network normal; Disk input/output is normal; CPU-High Monitor diagram The logs are not printing errors, but the TPS is very l

an execution plan, and stored in a database of SQL statements, is a collection of control flow language, the speed of course fast. 48, the return value of the function is not too large, this overhead is very large. A user-defined function that executes as a cursor consumes a large amount of resources if a large result is returned with a stored procedure. 49, as far as possible to avoid repeated access to the same or several tables, especially the lar

rownumObviously, this writing will result in reading the table first, then sorting, and then taking the first 5 records, the plan is as follows:If we write like this, the semantics are the same, but it saves a lot of reading and sorting costs:Select/*+ Index (T1,IDX1_T1) */* from T1 where rownumThe execution plan for this SQL is as follows:As you can see, the SQL does not follow the hint instructions and s

10.1 Order problems for connecting query tablesThe parser for SQL Server processes the table names in the FROM clause in a right-to-left order, so the table that is written in the FROM clause (the underlying table driving tables) will be processed first, and in the case of multiple tables in the FROM clause, the tables with the fewest number of record bars must be selected as the underlying table. When SQL

reduce"-"Map number: Bad man-made setting"-"Size of HDFs block: dfs.blocks.size=128mSize of Shard: minisize/maxsizeMapreduce.input.fileinputformat.split.minisize -"Enterprise Scenario"-"file large, less 200M 100 map by default block processing-"File small, multi 40M 400 map by Shard -Number of REUDCENumber of 0.95-1.75*node* containers -Native mode Local: Run the entire task on the current nodeConditions:1, the job input data size cannot exceed the default parametersinputbytes.size=128m2. Numbe

1. Check the database space usage to see which tables are consuming larger disk spaceExecute the following statement:SelectO.name, SUM (p.reserved_page_count) asReserved_page_count, SUM (p.used_page_count) asUsed_page_count, SUM ( CaseWhen (p.index_id2) Then (p.in_row_data_page_count+P.lob_used_page_count+p.row_overflow_used_page_count)Elsep.lob_used_page_count+P.row_overflow_used_page_count End) asDataPages, SUM ( CaseWhen (p.index_id2) then Row_countElse 0end) asrowcounts fromsys.dm_db_partiti

Label:In today's scale OLTP system, it is a good way to solve the problem by replicating multiple copies in order to alleviate the single point of reading and writing pressure in the database, especially the read pressure.The SQL Server transactional replication transactional Replication is the most common form of replication we take. Some of the previous articles always introduce some basic constructs,Lack of some introduction to the optimization, to

rationally;② Historical Data Quick cleanup: ALTER TABLE t truncate partition P1;.Disadvantages:① too many partitions also increase overhead, and in general, tables above the million data level are considered for partitioning.② too many partitions also result in a workload on partition maintenance.4. Index Organization table (index-organized Tables)The table itself is the index, and the index itself is the table. For configuration tables that are rarely updated.Pros: eliminate back tables and ap

if the amount of data is small, create a table and insert it in order to mitigate the resources of the system tables. If a temporary table is used, TRUNCATE TABLE first and then drop table when all temporary tables are finally explicitly deleted, which avoids longer locking of the system tables. Index You should first consider establishing an index on the columns involved in where and order by. When using an indexed field as a condition, if the index is a composite index

DISTINCTdatabase_id,object_idFrom Sys.dm_db_missing_index_details) as Ddmid on ddmid.database_id = ddios.database_idand ddmid.object_id = ddios.object_idWHERE Ddios.page_lock_wait_in_ms > 0 and object_name (ddios.[ OBJECT_ID]) like ' Pos_transmst 'ORDER by Ddios.page_lock_wait_count DESC;/*******************************************************************************************--page IO Latch Wait *******************************************************************************************/ SEL