Database Reference
In-Depth Information
Here is another formatted output in YAML:
warehouse_db=# EXPLAIN (FORMAT YAML) SELECT * FROM record.history;
QUERY PLAN
------------------------------
- Plan: +
Node Type: "Seq Scan" +
Relation Name: "history"+
Alias: "history" +
Startup Cost: 0.00 +
Total Cost: 1934580.00 +
Plan Rows: 100000000 +
Plan Width: 46 +
Planning Time: 0.088
(2 rows)
Cost parameters
The costs in PostgreSQL are measured in arbitrary units determined by the planner's
cost parameters usually measured in units of disk page fetches. The cost computation
is the estimated cost loosely associated with authentic real-world numbers. The
different type of cost parameters can be listed as follows:
seq_page_cost : This is the cost to fetch sequential disk pages. By default, the
cost in units of time to read is 8 K blocks, because by default, the page size is
8 K. By default, the value of this parameter is 1 ; hence, all other parameters
have a value relative to this parameter.
random_page_cost : This is a nonsequential read cost of disk page, that is, the
time required to get the random disk page. It is a multiple of the sequential
page cost ( seq_page_cost ). The default value is 4 .
cpu_tuple_cost : This is the cost of processing each tuple, that is, the time
needed to process a single row. The default value is 0.01 .
cpu_operator_cost : This is the cost of processing each operator or function
call; the default value is 0.0025 .
cpu_index_tuple_cost : This is the cost of processing each index entry
during an index scan; the default value is 0.005 .
 
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