Activate adaptive filtering in AlloyDB for PostgreSQL

This page describes adaptive filtering in AlloyDB.

Adaptive filtering analyzes query patterns and data distributions during query execution to dynamically choose the most efficient filtering strategy such as inline or pre-filtering.

The AlloyDB query optimizer uses cost-based analysis to determine whether inline filtering or pre-filtering provides the best performance at any given point during query execution.

Such optimization is beneficial for AlloyDB's filtered vector searches, where adaptive filtering automatically switches between vector and metadata index usage to ensure efficient and accurate results without your manual intervention.

Enable adaptive filtering

To enable adaptive filtering, use the scann.enable_preview_features flag.

When adaptive filtering triggers a switch from inline filtering to pre-filtering during execution, the query plan dynamically changes.

For example, the plan can show Bitmap assisted pre-filtering in the Execution Strategyfield when the optimizer determines that pre-filtering is more efficient at that point in the query. This dynamic change occurs as the system adapts to the actual data that it encounters during the query's execution.

  Limit 
  
 ( 
 actual 
  
 rows 
 = 
 10 
  
 loops 
 = 
 1 
 ) 
  
 - 
>  
 Custom 
  
 Scan 
  
 ( 
 vector 
  
 scan 
 ) 
  
 on 
  
 t1 
  
 ( 
 actual 
  
 rows 
 = 
 10 
  
 loops 
 = 
 1 
 ) 
  
 Execution 
  
 Strategy 
 : 
  
 Bitmap 
  
 assisted 
  
 pre 
 - 
 filtering 
  
 Order 
  
 By 
 : 
  
 ( 
 vec_col 
  
< = 
>  
 '[...]' 
 :: 
 vector 
 ) 
  
 Limit 
 : 
  
 10 
  
 Num 
  
 Requalifications 
 : 
  
 0 
  
 Num 
  
 filtered 
 : 
  
 1000 
  
 - 
>  
 Bitmap 
  
 Index 
  
 Scan 
  
 on 
  
 btree_idx 
  
 ( 
 actual 
  
 rows 
 = 
 10000 
  
 loops 
 = 
 1 
 ) 
  
 Index 
  
 Cond 
 : 
  
 ( 
 int_col 
  
< = 
  
 100000000 
 ) 
 

What's next

• Filtered vector search in AlloyDB