Contents
(hint-list)=
Hint list
The available hints are listed below.
| Group | Format | Description |
|:——|:—––|:————|
| Scan method | SeqScan(table)| Forces sequential scan on the table. |
| | TidScan(table) | Forces TID scan on the table. |
| | IndexScan(table[ index...]) | Forces index scan on the table. Restricts to specified indexes if any. |
| | IndexOnlyScan(table[ index...]) | Forces index-only scan on the table. Restricts to specified indexes if any. Index scan may be used if index-only scan is not available. |
| | BitmapScan(table[ index...])| Forces bitmap scan on the table. Restricts to specified indexes if any. |
| | IndexScanRegexp(table[ POSIX Regexp...])IndexOnlyScanRegexp(table[ POSIX Regexp...])BitmapScanRegexp(table[ POSIX Regexp...]) | Forces index scan, index-only scan (For PostgreSQL 9.2 and later) or bitmap scan on the table. Restricts to indexes that matches the specified POSIX regular expression pattern. |
| | NoSeqScan(table)| Forces to not do sequential scan on the table. |
| | NoTidScan(table)| Forces to not do TID scan on the table.|
| | NoIndexScan(table)| Forces to not do index scan and index-only scan on the table. |
| | NoIndexOnlyScan(table)| Forces to not do index only scan on the table. |
| | NoBitmapScan(table) | Forces to not do bitmap scan on the table. |
| Join method| NestLoop(table table[ table...]) | Forces nested loop for the joins on the tables specified. |
| | HashJoin(table table[ table...])| Forces hash join for the joins on the tables specified. |
| | MergeJoin(table table[ table...]) | Forces merge join for the joins on the tables specified. |
| | NoNestLoop(table table[ table...])| Forces to not do nested loop for the joins on the tables specified. |
| | NoHashJoin(table table[ table...])| Forces to not do hash join for the joins on the tables specified. |
| | NoMergeJoin(table table[ table...]) | Forces to not do merge join for the joins on the tables specified. |
| Join order | Leading(table table[ table...]) | Forces join order as specified. |
| | Leading(<join pair>)| Forces join order and directions as specified. A join pair is a pair of tables and/or other join pairs enclosed by parentheses, which can make a nested structure. |
| Behavior control on Join | Memoize(table table[ table...]) | Allows the topmost join of a join among the specified tables to Memoize the inner result. Not enforced. |
| | NoMemoize(table table[ table...]) | Inhibits the topmost join of a join among the specified tables from Memoizing the inner result. |
| Row number correction | Rows(table table[ table...] correction) | Corrects row number of a result of the joins on the tables specified. The available correction methods are absolute (#), addition (+), subtract (-) and multiplication (*). should be a string that strtod() can understand. |
| Parallel query configuration | Parallel(table <# of workers> [soft\|hard]) | Enforces or inhibits parallel execution of the specified table. <# of workers> is the desired number of parallel workers, where zero means inhibiting parallel execution. If the third parameter is soft (default), it just changes max_parallel_workers_per_gather and leaves everything else to the planner. Hard enforces the specified number of workers. |
| GUC | Set(GUC-param value) | Sets GUC parameter to the value defined while planner is running. |