Scan Operation Hints

Function

These hints specify a scan operation, which can be tablescan, indexscan, or indexonlyscan.

Syntax

[no] tablescan|indexscan|indexonlyscan(table [index])

Parameter Description

  • no indicates that the specified hint will not be used for a join.

  • table specifies the table to be scanned. You can specify only one table. Use a table alias (if any) instead of a table name.

  • index indicates the index for indexscan or indexonlyscan. You can specify only one index.

NOTE:
indexscan and indexonlyscan hints can be used only when the specified index belongs to the table.
Scan operation hints can be used for row-store tables, column-store tables, OBS tables, and subquery tables.

Example

To specify an index-based hint for a scan, create an index named i on the i_item_sk column of the item table.

create index i on item(i_item_sk);

Hint the query plan in Example as follows:

explain
select /*+ indexscan(item i) */ i_product_name product_name ...

item is scanned based on an index. The optimized plan is as follows:

Feedback
编组 3备份
    openGauss 2024-05-26 00:44:47
    cancel