Why should you use a query plan for database administration?

The query plan is generated by the optimizer to tell the DBMS engine how to access and process the data to perform the query. Because SQL is a declarative language, not an imperative one, we specify what results we want and don't specify how to get them. The optimizer decides which path to run it from.This path is named as query plan.

A query plan is a detailed roadmap generated by a DBMS execute a SQL query efficiently. It outlines the steps the system will employ to retrieve and process data. Query design is the second most important factor in application speed (right after table design). It can show you where you need an index (index design is the third most important factor in application speed) or where it is ignoring an index. It may tell you when to update statistics, which join to use; where to explore denormalization; or where to use embedded hints in the query. Oracle provides a plan table for query tuning; it will show you the time and cost for a query to run.

Using a query plan helps optimize database performance by analyzing and selecting the most efficient way to execute a query, reducing resource usage, and improving response time.

Using query plans is essential for effective database administration as it helps optimize performance, troubleshoot issues, allocate resources efficiently, and improve overall database management and scalability.

A Query Plan is an internal database object that is used by a DB server engine to execute a SQL statement (it contains a set of steps for a DB engine to be executed). When a DB server engine executes a SQL statement the very first time - it compiles a Query Plan for the very first execution. Further executions are using the existing plan. Query Plan can be visualized through SSMS, for example - so we can see/investigate it.

Using a query plan in database administration helps optimize database performance by providing insights into how queries are executed and identifying areas for improvement, such as inefficient indexes or poorly structured queries.

SQL Server Management Studio (SSMS): In Microsoft SQL Server, SSMS can display graphical query plans when executing queries. This visual representation helps in understanding the steps involved in query execution. SELECT * FROM HumanResources.Employee AS e INNER JOIN Person.Contact AS c ON e.ContactID = c.ContactID ORDER BY c.LastName; Shows the visual representation of how the query is executed, including operators used and their functions

in the Oracle database, there are several ways to generate query execution plans, such as AUTOTACE, EXPLAIN PLAN FOR select, DBMS_XPLAN.DISPLAY and use other tools like OEM or SQL Developer, however, each of them has Pros and Cons, for example, EXPLAIN PLAN FOR Provides a static plan without executing the actual SQL statement so the actual plan could be different, AUTOTRACE: we must run the query, sometimes it takes time. dbms_xplan.DISPLAY_CURSOR is a powerful tool which helps us to see the execution plan which exists in the shared pool(cursor) or AWR... V$SQL_PLAN: The V$SQL_PLAN dynamic performance view contains execution plan information for SQL statements in the shared SQL area.

Using SSMS: Open SSMS and connect to your SQL Server instance. Write your SQL query in the query editor window. Right-click anywhere within the query editor window. In the context menu, select one of the following options, depending on your desired level of detail: "Display Estimated Execution Plan" (Ctrl+L) "Include Actual Execution Plan" (Ctrl+M) Using T-SQL: SET STATISTICS ON; -- Your actual SQL query here SET STATISTICS OFF;

Os planos de consulta podem ser gerados através de comandos específicos em sistemas de gerenciamento de banco de dados, como o EXPLAIN no MySQL ou o Execution Plan no SQL Server.

Following below steps can be easy to read query plans: 1) Tree Structure: Visualize the plan as a tree, with operations as nodes. 2) Reading Order: Start from the rightmost node and read towards the left. 3) Icons: Each icon is a different operation in the query process. 4) Arrows: Follow the arrows to see the flow of data. 5) Thick Arrows: These indicate more data being processed. 6) Warnings: Yellow signs point to possible performance issues. 7) Cost Values: Help identify resource-heavy operations.

Bottom to top and right to left. See for thick arrows I. E with high amount of data (90% cases) , they are majorly due to developers using functions in where clause and due to which cardinality estimation doesn't happen resulting to whole index scan. Most of DBAs (98%) are not able to suggest the way of removing function from where clause as it needs query rewriting. Similarly check wether statistics are updated with full scan or not. Also do check auto update statistics are off in database setting. In index maintenance, for tables with high DML operations, indexes shall be rebuild (not reorganize) over a particular period of time as it leads to high fragmentation at leaf level nodes

Reading a query plan helps you understand how SQL Server executes a query and where it might be slow. Start at the End: Begin with the final result node. Follow the Arrows: Trace the path of data flow through the plan. Check Costs: Look at each step's estimated cost - lower is better. Compare Estimates with Reality: See if actual results match estimates. Spot Problems: Watch for high-cost operations like table scans or sorts. Understand Joins: Different join methods impact performance differently. Index Usage: Check if indexes are being used effectively. Identify Issues: Look for common problems like unnecessary sorts. Consider Reuse: Think about whether the plan can be reused efficiently.

#Query Plan plays a vital role in the performance tuning when a particular query is taking time. 1-Reading a query plan can be easier in terms of graphical representation. 2-Read from right to left or top to bottom in case of multiple branches. 3-Check few basic operators like clustered scan, key lookup & nested loop. 4-If we find the above operators we need to dig more on the query and try to minimize it so as to improve the plan. 5-It will also recommend a few things like missing index and query hints if it is missing. 6-We can also check the properties of each operator where there will be ample information like estimated & actual cost of the query etc.

Reading an execution plan that majorly have 2 ways, Graphical and Tree Structure. Graphical: Start with End, and go towards left, check all JOINs, Order, hover over arrow to see how many rows were estimated vs actual rows, check if plan is parallel or serial (parallel are with yellow parallel arrows), notice their cost (however it is not always a real indicator of whole thing). Check warnings, red alerts, could be an indication of bad join or stale stats. Tree: Go to the middle portion, and start going upwards, it will have details of cost, index usage, stats etc.

Once you've generated and analyzed a query plan in SQL Server, you can leverage the insights to optimize your query for better performance. Here are some strategies to consider: 1. Address Inefficient Access Methods: Full Table Scans: Inefficient Index Seeks: 2. Optimize Join Order: The order in which tables are joined can significantly impact performance. Analyze the join conditions and table sizes: Smaller Tables First: Equality Joins Before Inequality Joins: 3. Improve Filtering Strategy: Early Filtering: Indexed Columns: 4. Optimize Aggregations: Complex Aggregations: Materialized Views: 5. Leverage Sorting Techniques: ORDER BY with Existing Indexes: Alternatives to Sorting:

- Use EXPLAIN and EXPLAIN ANALYZE to review query plans. - Create indexes on key columns, choose correct type (B-tree, GIN, etc.). - Use partial and multi-column indexes for specific filters. - Write queries efficiently: select only needed columns, filter early with WHERE, mindful JOIN order. - Consider partitioning for large tables and materialized views for complex queries. - Adjust PostgreSQL settings (work_mem, shared_buffers). - Regularly run VACUUM and ANALYZE for maintenance. - Stay updated with the latest PostgreSQL version. - Test changes in a staging environment before production.

Com base no plano de consulta gerado, é possível identificar oportunidades de otimiza??o, como a cria??o de índices adequados, reescrita de consultas para melhorar a eficiência ou ajuste de parametros de configura??o do banco de dados

Check the whole plan, look at all JOINs, understand how much of data are you dealing with, does it justify the amount of data JOINs bring with arrow details, do you see bad joins like forever running nested loop of LEFT joins, expensive sort operations, key lookup can be solved by covering index, index scan could be resolved by stats updates.

Query plans provide I sights into how the database executes a particular query, examples SQL. By analyzing the query plan, we can identify potential bottlenecks and. inefficient operations SQL: EXPLAIN SELECT, column1, column2 FROM table1 WHERE condition = 'value' From here we can such things as I mentioned above such as inefficient operations and bottleneck issues. To optimize from here, we can create an index on the condition column(s). This will help speed up queries that filter the data based upon the 'condition'. Making the database quicker and efficient. SQL: CREATE INDEX idx_condition ON table1(condition) Now we have the revised query!!

SQL Server has come up with QueryStore which is big change in SQL Server, most of the time if you keep stats, indexes proper, DON'T try to dominate optimizer if you don't understand the whole operation and understanding. QueryStore help you analyze plans, compare and carefully force the plan.

A automa??o de planos de consulta pode ser feita através de ferramentas de monitoramento de desempenho e otimiza??o de consultas, que podem identificar automaticamente problemas de desempenho e sugerir solu??es

Considering DB performance from Database Administration point of view is always challenging task. Some times good Execution plan is not worked. Actually DB execution plan is working fine but business & application stakeholder are not satisfied. So Application, Developer , Business stakeholder and DB Admin should be in line with requirement accordingly. Sometimes bottlenecks not in query tuning, it is in our understanding. Good performance and business demand both has to be mutually understood.

In SQL server you can use a feature called a live execution plan which is similar to a query plan but it updates in real time while our long-running query is executing. You can see it by observing the plan where are the bottlenecks and which tables have huge data that is making the query go slower.

People often seem to forget about DB maintenance, including reviewing and optimizing database indexes, monitoring system performance, and addressing potential bottlenecks or maybe there is in general no time for that :) Also, implementing database backup and recovery procedures is A MUST for data protection and disaster recovery. Ultimately, one would need to think about system updates and how these affect the status of a system in order to avoid your system to become a 'legacy' xD.

Ao utilizar um plano de consulta de forma eficaz, os administradores de banco de dados podem melhorar o desempenho, a escalabilidade e a confiabilidade do sistema, garantindo uma opera??o mais eficiente e otimizada. é uma prática essencial para garantir um bom funcionamento do banco de dados e uma experiência satisfatória para os usuários finais.