This feature is particularly useful for third-party applications where we don’t have access to the source code.īatch Optimize automatically identifies and optimizes problematic SQL statements using batch processing. Plan Control mode lets us take advantage of the SQL Plan Management feature introduced in Oracle 11g to optimize execution plans and deploy plan baselines for SQL statements without changing the original source code. SQL Rewrite mode allows us to generate SQL statements and index alternatives for problematic SQL statements. Optimize SQL offers SQL Rewrite mode and Plan Control mode. If we want to deactivate this window, we uncheck the "Show Welcome on next startup" option at the bottom of window. When we open this tool, we can see the Welcome window that shows us a list of tasks. It provides index recommendations for multiple SQL statements, simulates index impact analysis, and generates SQL execution plan alternatives. SQL Optimizer also provides a complete solution for index optimization and analysis of plan changes. Once SQL Optimizer identifies problematic SQL statements, it optimizes the SQL and provides replacement code that includes the optimized statement. SQL Optimizer analyzes, rewrites, and evaluates SQL statements located within database objects, files, or collections of SQL statements from Oracle's System Global Area (SGA). Here's a SQL Optimizer success story! SQL Optimizer for Oracle automates the SQL optimization process and maximizes the performance of our SQL statements. It is time to start using OPTIMIZER TRACE, and particularly in 5.7 ditch EXPLAIN for EXPLAIN FORMAT=JSON. We can now say "this join is expensive", which is a much better distinction By including the cost information in EXPLAIN we get all users to speak the same language. I have heard many users say "joins are slow", but a broad statement like this misses magnitude. These queries are not identical in cost even though they are in EXPLAIN output. With the FORMAT=JSON output also showing cost, we can see that two ranges costs 10.04, versus one big range costing 9.04 (not shown). The optimizer trace output shows that the first query executes as one range, while the second and third execute as 5 separate single-value ranges: SELECT * FROM film WHERE film_id =1 or film_id=2 or film_id=3 or film_id=4 or film_id=5. SELECT * FROM film WHERE film_id IN (1,2,3,4,5). SELECT * FROM film WHERE film_id BETWEEN 1 AND 5.Here are the outputs for the three versions of the query: You enable the optimizer trace, then you run the actual query.It doesn't just show the intended execution plan, it shows the alternative choices.It is similar to EXPLAIN, with a few notable differences: Optimizer trace is a new diagnostic tool introduced in MySQL 5.6 to show how the optimizer is working internally. There are now a couple of useful features to show the difference Optimizer Trace row ********* id: 1select_type: SIMPLEtable: film partitions: NULL type: rangepossible_keys: PRIMARYkey: PRIMARYkey_len: 2ref: NULL rows: 5 filtered: 100.00Extra: Using where Mysql> EXPLAIN SELECT * FROM film WHERE film_id BETWEEN 1 AND 5/Gmysql> EXPLAIN SELECT * FROM film WHERE film_id IN (1,2,3,4,5)/Gmysql> EXPLAIN SELECT * FROM film WHERE film_id =1 or film_id=2 or film_id=3 or film_id=4 or film_id=5/G********* 1. Here is an example using the sakila schema: All of the queries resolve to the same output in EXPLAIN. It is an interesting question because there was no good way to answer it when it was asked in 2009. WHERE someFIELD = 1 OR someFIELD = 2 OR someFIELD = 3. I am wondering if there is any difference in regards to performance between the following: I accidentally stumbled upon this Stack Overflow question this morning:
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |