top 10 optimizer

your homepage display speed will theoretically be 8 times times faster than the original speed.The word "theoretically" is mentioned here because if your clustered index is still blindly built on the primary key of the ID, your query speed is not so high, even if you set the index (non-aggregated index) on the "Date" field. Let's take a look at the speed performance of various queries in the case of 10 million data volumes (data in 3 months is 250,00

This article mainly introduced the detailed Pytorch batch training and the optimizer comparison, introduced in detail what is the Pytorch batch training and the Pytorch Optimizer optimizer, very has the practical value, needs the friend to consult under First, Pytorch batch training 1. Overview Pytorch provides a tool to wrap data in batches for training--datalo

target SQL statement as its execution plan, and the judgment principle used by CBO is cost, CBO selects the least cost from the many possible execution paths of the target SQL statement as its execution plan. The cost values of each execution path are based on the tables and indexes involved in the target SQL statement, the statistical information of related objects such as columns is calculated. During the parsing process, ORACLE will check the syntax, semantics, and permissions of the targ

for execution, subsequent execution will happen soon, because Oracle recognizes the same SQL statement and reuse the execution of those statements. However, for systems that generate special SQL statements or SQL statements embedded with text variables, the generation time of the SQL Execution Plan is very important, and the previous execution plan cannot be reused. For queries that connect many tables, Oracle needs to spend a lot of time checking the proper order of these tables. Evaluation Ta

",10)) USERYES How does extended statistics help the optimizer? The following example demonstrates how the extended statistical information helps the optimizer correctly evaluate the selectivity of SQL statements, SQL> Select * From User_Stat_Extensions; -- no extended statistics is enabled. No row is selected. SQL> exec dbms_stats.gather_table_stats ('sh', 'c

example, the predicate condition in the original target SQL is "T1.c1=t2.c1 and T2.c1=t3.c1", then the CBO may add "T1.C1=T3.C1" in this predicate condition, that isModified to "T1.c1=t2.c1 and T2.c1=t3.c1 and T1.c1=t3.c1"③: outer JOIN predicate deliveryFor example, the predicate condition in the original target SQL is "T1.C1=T2.C1 (+) and t1.c1=10", then the CBO may add "t2.c1 (+) =10" in this predicate c

/directory (the version may be different, so use PHP under Zend. INI file ), Solve the problem... In addition: 1. Copy the php. ini file from the Linux system directory to your PHP installation root directory.2. Select Your PHP root directory if you specify the INI file when installing Zend optimizer.3. After the installation is complete, Zend optimizer will be OK. Recently, some projects have to

As with Oracle databases, the DB2 database also uses an optimizer to analyze your SQL and generate the execution plan that it considers optimal (Access plans). The DB2 optimizer is actually a collection of standard Rules, and in general we just tell DB2 what to retrieve, not how to retrieve it. So what does the DB2 optimizer do to determine the optimal access pa

other value '; Assume that the test on col1 matches 900 data rows, the test on col2 matches 300 data rows, and the test at the same time only has 30 data rows. First, test Col1 and there will be 900 data rows. check them to find 30 matching records with the values in col2, and 870 of them will fail. First, test col2 will have 300 data rows. check them to find 30 records matching the values in col1. only 270 of the records failed, therefore, less computing and disk I/O are required. The result i

row, each external column executes a range optimizer), and if this option is turned off, only the first call to Join_tab::sql_select is tracked Repeated_ Subselect: subquery, if closed, only the first call to Item_subselect is tracked —————————————————-TODO PLAN: Increase the threshold (number of rows read, or time of execution), when the threshold is exceeded, The trace is automatically imported into a file, which makes it easy to debug online. Refe

Label: HTTP ar strong SP on 2014 BS ad A Liang is an optimizer with 10 years of Seo experience. He stepped into the industry in 2004 and resigned in 2013 and made his own private order optimization, from the beginning of the good income to the following struggling, in through the cloud customer network to receive a ticket, now more than yuan in the month, the following will share the masters of this bitte

of PHP 4.3.X, before the correct installation, or will say that the version does not support. I'm installing it to C:\Inetpub\Zend. The Zend Optimizer Installation Wizard automatically modifies the php.ini to help you start the engine based on your selections. The following is a brief introduction to the configuration options for Zend Optimizer. The following is the default configuration code in the php.i

matches 900 rows of data, the test on col2 matches 300 rows of data, while the test at the same time gets only 30 rows of data. Test Col1 will have 900 rows of data, you need to check that they find 30 of them and col2 in the matching records, 870 of which failed. Test col2 will have 300 rows of data, you need to check that they found 30 of them and the values in the col1 matching records, only 270 failed, so need less calculation and disk I/O. As a result, the

oracle| Performance | optimization Improving Oracle performance limits with the Smart Optimizer The time spent preparing new SQL statements is the most important component of the execution time for Oracle SQL statements. But by understanding the mechanism within Oracle to generate execution plans, you can control the amount of time that Oracle spends evaluating the connection order and can improve query performance in general. Preparing to execute an

, future execution will occur quickly because Oracle approves the same SQL statement and reuses the execution of those statements. However, for systems that generate special SQL statements or SQL statements that embed literal variables, the generation time of the SQL execution plan is important, and the previous execution plan is often not reusable. For queries that are connected to many tables, Oracle takes a significant amount of time to detect the appropriate sequence of connections to those

match the index, but the order of the indexed columns is important.Like what:SELECT * FROM test where user_name= ' test1 ' and sex>0 and the age =10?select * from Test where sex>0 and User_name= ' test1 ' and ' =10?select * from Test where age =10 and User_name= ' test1 ' and sex>0　　Can all be matched to the name_sex_age index3. Complex predicate like predicateI

Tags: interference with other indexes after MySQL order by causes Optimizer to go wrong indexMySQL version:5.5.36[email protected] 5.5.36-log XXX 10:19:54>show index from fd_finance_acc_his;+--------------------+------------+------------------------+--------------+--------------+-----------+--------- ----+----------+--------+------+------------+---------+---------------+| Table | Non_unique | Key_name | Seq

Tags: style c int a data use1. The optimizer (Optimizer) is an optimization tool for SQL analysis and execution that is responsible for making the SQL execution plan, which is responsible for ensuring that SQL performs the most efficiently, such as determining how Oracle accesses the data, full table scan, or index range Range scan), or full index quick Scan (index fast, index_ffs), and how the query is ass

To make this query more efficient, add an index to one of the join columns and rerun the explain statement: mysql> ALTER TABLE t2 ADD INDEX (i2);mysql> EXPLAIN SELECT t1.i1, t2.i2 FROM t1, t2 WHERE t1.i1 = t2.i2\G*************************** 1. row ***************************id: 1select_type: SIMPLEtable: t1type: ALLpossible_keys: NULLkey: NULLkey_len: NULLref: NULLrows: 1000Extra:*************************** 2. row ***************************id: 1select_type: SIMPLEtable: t2type: refpossible_key

The MySQL query optimizer has several goals, but the primary goal is to use the index as much as possible, and use the most restrictive indexes to eliminate as many rows of data as possible.Your ultimate goal is to submit a SELECT statement to find rows of data instead of excluding rows of data. The reason the optimizer tries to exclude rows of data is that the faster it excludes rows of data, the faster it