DISABLE_HBASE_NUM_ROWS_ESTIMATE Query Option

Use the DISABLE_HBASE_NUM_ROWS_ESTIMATE query option to disable key sampling of HBase tables in row count and row size estimation.

While generating a plan for an HBase query, the planner samples the underlying HBase tables to estimate their row count and row size, and the sampling can negatively impact the planning time. When the HBase table stats does not change much in short time, disable the sampling by setting the DISABLE_HBASE_NUM_ROWS_ESTIMATE query option to TRUE. And Impala planner will fall back to using Hive Metastore (HMS) table stats instead.

When DISABLE_HBASE_NUM_ROWS_ESTIMATE query option is set to TRUE, you need to update the HMS table stats by running COMPUTE STATS. Alternatively, you can manually set table statistics by running ALTER TABLE. See Table and Column Statistics for details.

The following values are supported:

• TRUE or 1: Disables the normal key sampling of HBase tables and uses HMS table stats for estimation.
• FALSE or 0: Enables the normal sampling of HBase tables.

Type: BOOLEAN

Default: FALSE

Parent topic: Query Options for the SET Statement