AMashenkov commented on code in PR #5987: URL: https://github.com/apache/ignite-3/pull/5987#discussion_r2131918664
########## docs/_docs/sql-reference/explain-help-with-performance-problems.adoc: ########## @@ -0,0 +1,495 @@ +// Licensed to the Apache Software Foundation (ASF) under one or more +// contributor license agreements. See the NOTICE file distributed with +// this work for additional information regarding copyright ownership. +// The ASF licenses this file to You under the Apache License, Version 2.0 +// (the "License"); you may not use this file except in compliance with +// the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. += How to use EXPLAIN command to identify possible SQL execution performance problems + +SQL EXPLAIN is a powerful command used to analyze and understand the execution plan of a query without actually executing it. +Using EXPLAIN, shows the query execution plan, which includes details such as: + +- The order in which tables are accessed. +- The type of join operations used (e.g., nested loop, hash join, merge join). +- Any indexes that are used to speed up data retrieval. +- Estimated costs and row counts for different parts of the query. + +This information is crucial for optimizing query performance, identifying bottlenecks, and making informed decisions about database schema design and indexing strategies. + +SQL EXPLAIN output analysis can help to optimize slow queries execution. Frequent bottlenecks in SQL execution as follows: + +- Avoid scanning an entire table, which is frequently the slowest way to access data. +- Avoid scanning non-optimal indexes. +- Planner related issues. Review Comment: What are "planner related issues"? Maybe it make sense to mention non-optimal JOIN order or JOIN algo. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: notifications-unsubscr...@ignite.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
