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Poor performance with Connect for ODBC MongoDB Driverr when using joins

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TitlePoor performance with Connect for ODBC MongoDB Driverr when using joins
URL Namepoor-performance-with-connect-for-odbc-mongodb-driverr-when-using-joins
Article Number000112474
EnvironmentProduct: Connect for ODBC MongoDB Drver
Version: 7.1
OS: All Supported
Database: MongoDB
Application: N/A
Question/Problem Description
When executing a statement with join syntax, the performance in some instances is slow.
Steps to Reproduce
Clarifying Information
Error Message
Defect Number56352
Enhancement Number
Cause
MongoDB doesn’t support JOINS across native collections, so the driver has to provide that functionality through its internal SQL engine. This will always be expensive, unless the tables being joined are stored within the same native table (i.e. if a parent-child relationship exists, performance is much better since this can be executed as a single query to the server). 

When using the [INNER] JOIN … ON … syntax, the optimizer assumes that the order of the tables matters or at least is determined by the user to give the best performance. With JOINs if the order of tables is specified in order from least number of rows to most number of rows, then a query with JOIN syntax will complete quickly.
 
Resolution
There are two options for resolving the slow performance:
  1. Optimize the query to get the best performance (order of tables should be smallest number of rows to highest number of rows) 
  2. Ensure that a parent-child relationship exists between the tables
Workaround
Replace the JOINs with commas
Notes
Last Modified Date11/23/2016 12:31 AM
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