Troubleshoot ScaNN index errors

List of errors

The following a list of errors that are generated when you try to create a ScaNN index. You can disable generation of these errors and continue to generate the index. For more information, see Enforce index creation and suppress errors .

ERROR: Cannot create ScaNN index with empty table

Error message

When you try to generate an index on a table with no data or try to truncate a table with a ScaNN index generated on it, the following error occurs:

ERROR: Cannot create ScaNN index with empty table. Once the table is populated with data, create the index. See documentation to bypass this validation.

Sample queries that cause the error

• Query Example A

    create 
    
   table 
    
   t1 
    
   ( 
   a 
    
   INT 
   , 
    
   b 
    
   VECTOR 
   ( 
   512 
   )); 
   CREATE 
    
   TABLE 
   create 
    
   index 
    
   on 
    
   t1 
    
   using 
    
   ScaNN 
   ( 
   b 
    
   cosine 
   ) 
    
   with 
    
   ( 
   num_leaves 
    
   = 
    
   10 
   , 
    
   quantizer 
    
   = 
    
   'sq8' 
   ); 
   
  

• Query Example B

    truncate 
    
   t1 
   ; 
   
  

Recommended fix

Make sure that your table is populated with embedding vectors before you generate a ScaNN index.

ERROR: Cannot create ScaNN index

Error message

When you try to generate an index on a table with few rows populated, the following error occurs:

Cannot create ScaNN index, error: INVALID_ARGUMENT: Number of row (5) must be larger than (1000).

Sample query that causes the error

  create 
  
 table 
  
 t1 
  
 ( 
 a 
  
 INT 
 , 
  
 b 
  
 VECTOR 
 ( 
 512 
 )); 
 CREATE 
  
 TABLE 
 insert 
  
 into 
  
 t1 
  
 select 
  
 ( 
 random 
 () 
 * 
 1 
 e9 
 ):: 
 int 
 , 
  
 random_vector 
 ( 
 512 
 ) 
  
 from 
  
 generate_series 
 ( 
 1 
 , 
  
 5 
 ); 
 INSERT 
  
 0 
  
 5 
 create 
  
 index 
  
 on 
  
 t1 
  
 using 
  
 scann 
 ( 
 b 
  
 cosine 
 ) 
  
 with 
  
 ( 
 num_leaves 
  
 = 
  
 100 
 , 
  
 quantizer 
  
 = 
  
 'sq8' 
 ); 
 

Recommended fix

Ensure that your table is populated with embedding vectors before you generate a ScaNN index. We recommend that the number of rows in the table are greater than the value defined in the num_leaves parameter.

ERROR: Cannot create ScaNN index on parent partition table.

Error message

If you have created partitioned tables from a parent table, then creating a ScaNN index on the parent table generates the following error:

ERROR: Cannot create ScaNN index on parent partition table. Create ScaNN indexes on the child tables instead. See documentation to bypass this validation.

Sample query that causes the error

  create 
  
 table 
  
 t1 
  
 ( 
 a 
  
 INT 
 , 
  
 b 
  
 VECTOR 
 ( 
 512 
 )) 
  
 partition 
  
 by 
  
 range 
 ( 
 a 
 ); 
 CREATE 
  
 TABLE 
 CREATE 
  
 TABLE 
  
 t1_one_ten 
  
 PARTITION 
  
 of 
  
 t1 
  
 for 
  
 values 
  
 from 
  
 ( 
 1 
 ) 
  
 to 
  
 ( 
 10 
 ); 
 CREATE 
  
 TABLE 
 insert 
  
 into 
  
 t1_one_ten 
  
 select 
  
 ( 
 random 
 () 
 * 
 1 
 e9 
 ):: 
 int 
 , 
  
 random_vector 
 ( 
 512 
 ) 
  
 from 
  
 generate_series 
 ( 
 1 
 , 
  
 100 
 ); 
 INSERT 
  
 0 
  
 100 
 CREATE 
  
 TABLE 
  
 t1_eleven_twenty 
  
 PARTITION 
  
 of 
  
 t1 
  
 for 
  
 values 
  
 from 
  
 ( 
 11 
 ) 
  
 to 
  
 ( 
 20 
 ); 
 CREATE 
  
 TABLE 
 insert 
  
 into 
  
 t1_eleven_twenty 
  
 select 
  
 ( 
 random 
 () 
 * 
 1 
 e9 
 ):: 
 int 
 , 
  
 random_vector 
 ( 
 512 
 ) 
  
 from 
  
 generate_series 
 ( 
 1 
 , 
  
 100 
 ); 
 INSERT 
  
 0 
  
 100 
 create 
  
 index 
  
 on 
  
 t1 
  
 using 
  
 scann 
 ( 
 b 
  
 cosine 
 ) 
  
 with 
  
 ( 
 num_leaves 
  
 = 
  
 10 
 , 
  
 quantizer 
  
 = 
  
 'sq8' 
 ); 
 

Recommended fix

You can't generate a ScaNN index on the parent table of a partitioned table. You must generate the ScaNN indexes on the partitioned table.

Enforce index creation and suppress errors

You can enforce AlloyDB to generate an index and suppress errors. Before allowing index generation with this method, consider the following implications:

• Since the index is trained on less or no data, centroids learn on zero data leading to bad recall.
• The write performance to the database might also be slow.

To force index generation, complete the following:

1. Set the scann.allow_blocked_operations creation session-level parameter to true on the database:

     SET 
     
    scann 
    . 
    allow_blocked_operations 
     
    = 
     
    true 
    ; 
    
   

2. Assign the SUPERUSER privilege to the user that will run these queries on the database:

     CREATE 
     
    USER 
     
     USER_NAME 
    
     
    WITH 
     
    SUPERUSER 
     
    PASSWORD 
     
     PASSWORD 
    
    ; 
    
   

   Replace the following:

   • USER_NAME : the name of the user you want to grant the privilege to.
   • PASSWORD : the password of the user.