Ways to Optimize SQL Queries with EXPLAIN In PostgreSQL
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Some web developers focus on the graphics and the design while the others can create dynamic systems using all the scripting languages and the databases. While creating large portals, it is essential to pay attention on the database designs. The Postgre EXPLAIN command can act as an important tool for investigating your SQL queries. All your web server logs can contain these commands. The slow query can activate re-run operations with the EXPLAIN command in the Oracle EPM. You can also monitor all the activities of the Postgres which is continuing behind the system.
Postgres Server: If you observe one line of command like this:
Seq Scan in vehicles (cost = 0.00 102401. 77 rows = 49 width =943)
It represents the server has identified all the requirements of the sequential sets of results. When you observe ‘Seq Scan’, it is more likely that some indexes are missing in the SQL server.
EXPLAIN Command: You can check out all your queries that are running with EXPLAIN. From the Postgres command, we already know that Seq Scan can successfully run through the vehicle results list. A proper index is required in the company_id to find out the components through the WHERE clause of the query.
Filter Line: When you reach deep inside the logs, you can see the Filter line. It is essential for finding out the columns through the WHERE clause and the index are required for the successful functioning.
Rails Migration: For adding the index, the Rails migration function can be used like the command create_index. After the creation of the migration tool, the Query can speed up and the EXPLAIN function can no longer be activated in the server logs.
ActiveRecord: If your application is running during the production process, the ActiveRecord can easily be activated. It will not perform for the re-run activities of the slow queries. The EXPLAIN command can work on the slow query again and again until it gains the complete output according to the database generation.
Slow Query Analyzer: This is the function of the ActiveRecord where the re-run can be done through the application. You can increases the speed of your SQL queries with the help of the EXPLAIN command.
Indexes: When you are creating a large database, the index can serve a lot of purposes. If the columns can be declared as the primary keys, the indexes are created by default. In all the other cases, you will have to create the index on your own. You should be creating the indexes in the columns where you are repeatedly using the WHERE clause from your queries. The column names can repeatedly be used in the ‘on’ component of the join clauses. But over indexing is not at all advised. . Over indexing can slow down the whole process. So you can only create the index where it is required.
Multiple Row Insert Statement: If you can use the multiple row insert statement, the index gets automatically updated when a record gets inserted. So, a large number of records can be inserted at once and the index gets updated with them.
Sub-queries: The sub queries can be used instead of the joins, so that you are not required to insert the field values in the second table. The sub queries are also faster than the joins functions.
There are also some other ways through which you can optimize the SQL queries. EXPLAIN is one of the most important among them. This is a very easy method for instantly fixing the performance problems of your server. Depending on the size of your database, you are required to optimize your SQL queries.
Bio: Jack Dawson is
a well known SQL expert who has been working with Oracle
EPM for a long time.
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