Table Sample Scan
Short Description
The Sample Table Scan node indicates a TABLESAMPLE query running
Detailed Description​
The Sample Table Scan node indicates a TABLESAMPLE query running. PostgreSQL 9.5 introduced the ability to retrieve a sample of rows from large tables using either a random method (SYSTEM) or the BERNOULLI method. The BERNOULLI method gives a better distribution of data as it scans the whole table and returns random rows (tuples), whereas the SYSTEM method is faster as it selects random pages and returns all their rows.
Additional Links​
- PostgreSQL Documentation - Using Explain
- pgAnalyze - Explain
- eTutorials - Understanding How PostgreSQL Executes a Query
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