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Ru, Li Yi 0b0c254b4c gaussdb_umn_1128

Reviewed-by: Wagner, Fabian <fabian.wagner@t-systems.com>
Co-authored-by: Ru, Li Yi <liyiru7@huawei.com>
Co-committed-by: Ru, Li Yi <liyiru7@huawei.com>

2025-01-13 14:51:57 +00:00

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Stream Operation Hints

Description

These hints specify a stream operation, which can be broadcast or redistribute.

Syntax

[no] broadcast|redistribute(table_list)

Parameter Description

no specifies that the specified hint will not be used for a stream operation.
table_list indicates tables to be joined for a stream operation. For details, see Parameter description.

Example

Hint the query plan in Example as follows:

explain 
select /*+ no redistribute(store_sales store_returns item store) leading(((store_sales store_returns item store) customer)) */ i_product_name product_name ...

In the original plan, the join result of store_sales, store_returns, item, and store is redistributed before it is joined with customer. After the hinting, the redistribution is disabled and the join order is retained. The optimized plan is as follows:

Parent topic: Hint-based Tuning

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