In this video, discover when queries can have steps executed in parallel.
- [Instructor] Another way to make queries … execute faster is to execute steps in parallel. … Sometimes the execution plan builder will find … that it can run some steps in parallel. … In that case, it may try to execute parts … of the plan in parallel, … and then combine the results together. … You can tell your execution plan is running … in parallel if there is a GATHER … or GATHER MERGE in the query plan. … Steps below the GATHER or GATHER MERGE … are executed in parallel. … How many parallel processes the execution plan … will use is based on a couple of parameters, … the max parallel workers and the max … worker process parameters. … Now these are Postgres-specific parameters, … but if your database supports parallel queries, … it's likely to have something similar. … In order for a query to execute some steps … in parallel, we need to have the max parallel … workers per gather parameter set to a value … greater than zero, the dynamic shared … memory type parameter must not be set to none, …
Author
Dan Sullivan
Released
4/1/2019- How SQL executes queries
- Working with PostgreSQL tools for tuning
- Bitmap and hash indexes
- Using different types of indexes to improve performance
- Challenges with joining tables
- When to use partitioning to improve performance
- Collecting statistics about data in tables
Skill Level Advanced
Duration
Views
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Introduction
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1. How SQL Executes a Query
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Scanning tables and indexes3m 12s
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Joining tables2m 24s
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Partitioning data2m 23s
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2. PostgreSQL Tools for Tuning
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Installing PostgreSQL2m 41s
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Overview of pgAdmin3m 21s
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Explain and analyze3m 37s
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Indexes3m 7s
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3. Types of Indexes
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Indexing3m 1s
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B-tree indexes2m 2s
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B-tree index example plan2m 18s
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Bitmap indexes1m 46s
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Bitmap index example plan2m 39s
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Hash indexes1m 19s
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Hash index example plan1m 32s
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PostgreSQL-specific indexes1m 17s
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4. Tuning Joins
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Nested loops3m 19s
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Nested loop example plan3m 55s
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Hash joins1m 25s
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Hash join example plan1m 57s
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Merge joins2m 17s
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Merge join example3m 16s
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Subqueries vs. joins1m 11s
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5. Partitioning Data
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Partition by range2m 6s
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Partition by list1m 37s
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Partition by list example4m 55s
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Partition by hash2m 12s
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Partition by hash example4m 51s
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6. Materialized Views
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Materialized views1m 41s
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7. Other Optimization Techniques
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Hints to the query optimizer2m 13s
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Parallel query execution2m 3s
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Miscellaneous tips1m 47s
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Conclusion
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Next steps41s
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Video: Parallel query execution