In this video, explore scanning operations and learn how to improve on scanning with indexes.
- [Narrator] Let's turn out attention … to scanning tables and indexes. … One of the simplest operations … in an execution plan is a scan operation. … This is basically the process … of accessing each row in a table. … We can also scan indexes, … which, really, are a special kind of table. … Scanning is a linear operation, … moving from one row to the next, … and performing some operation, … like applying a filter to implement a WHERE clause. … Scanning is simple. … The database fetches data blocks … from persistent storage or cache, … applies a filter, join, or other operation on the row, … and then moves on to the next row. … The time it takes to finish the scan is based … on the number of rows in the table. … Now, I should say, it's not always that simple. … Data is not always stored in a row-based fashion. … Column-based storage is used in data warehouse … and other big data applications. … This can make filtering based on the value … of a single or small number of columns … quite efficient when working with large tables. …
Author
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: Scanning tables and indexes