Google Git
Sign in
apache / impala / 8a582472527eb7300cf5e855d401a90e662de556 / . / docs / build / asf-site-html / topics / impala_disable_hbase_num_rows_estimate.html
blob: 24a1d9eb5f7fd0d957e4bf5a30bf9677527e1a49 [file] [log] [blame]
<!DOCTYPE html
SYSTEM "about:legacy-compat">
<html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta charset="UTF-8"><meta name="copyright" content="(C) Copyright 2023"><meta name="DC.rights.owner" content="(C) Copyright 2023"><meta name="DC.Type" content="concept"><meta name="DC.Relation" scheme="URI" content="../topics/impala_query_options.html"><meta name="prodname" content="Impala"><meta name="version" content="Impala 3.4.x"><meta name="DC.Format" content="XHTML"><meta name="DC.Identifier" content="disable_hbase_num_rows_estimate"><link rel="stylesheet" type="text/css" href="../css/commonltr.css"><link rel="stylesheet" type="text/css" href="../css/dita-ot-doc.css"><title>DISABLE_HBASE_NUM_ROWS_ESTIMATE Query Option</title></head><body id="disable_hbase_num_rows_estimate"><header role="banner"><!--
The DITA Open Toolkit is licensed for use under the the Apache
Software Foundation License v2.0.
A copy of the Apache Software Foundation License 2.0 is
available at http://opensource.org/licenses/apache2.0.php
This statement must be included in any copies of DITA Open
Toolkit code.
--><div class="header">
<p>Apache Impala</p>
<hr>
</div></header><nav role="toc"><ul><li><a href="../topics/impala_intro.html">Introducing Apache Impala</a></li><li><a href="../topics/impala_concepts.html">Concepts and Architecture</a></li><li><a href="../topics/impala_planning.html">Deployment Planning</a></li><li><a href="../topics/impala_install.html">Installing Impala</a></li><li><a href="../topics/impala_config.html">Managing Impala</a></li><li><a href="../topics/impala_upgrading.html">Upgrading Impala</a></li><li><a href="../topics/impala_processes.html">Starting Impala</a></li><li><a href="../topics/impala_tutorial.html">Tutorials</a></li><li><a href="../topics/impala_admin.html">Administration</a></li><li><a href="../topics/impala_security.html">Impala Security</a></li><li><a href="../topics/impala_langref.html">SQL Reference</a><ul><li><a href="../topics/impala_comments.html">Comments</a></li><li><a href="../topics/impala_datatypes.html">Data Types</a></li><li><a href="../topics/impala_literals.html">Literals</a></li><li><a href="../topics/impala_operators.html">SQL Operators</a></li><li><a href="../topics/impala_schema_objects.html">Schema Objects and Object Names</a></li><li><a href="../topics/impala_transactions.html">Transactions</a></li><li><a href="../topics/impala_langref_sql.html">SQL Statements</a><ul><li><a href="../topics/impala_ddl.html">DDL Statements</a></li><li><a href="../topics/impala_dml.html">DML Statements</a></li><li><a href="../topics/impala_alter_database.html">ALTER DATABASE</a></li><li><a href="../topics/impala_alter_table.html">ALTER TABLE</a></li><li><a href="../topics/impala_alter_view.html">ALTER VIEW</a></li><li><a href="../topics/impala_comment.html">COMMENT</a></li><li><a href="../topics/impala_compute_stats.html">COMPUTE STATS</a></li><li><a href="../topics/impala_create_database.html">CREATE DATABASE</a></li><li><a href="../topics/impala_create_function.html">CREATE FUNCTION</a></li><li><a href="../topics/impala_create_role.html">CREATE ROLE</a></li><li><a href="../topics/impala_create_table.html">CREATE TABLE</a></li><li><a href="../topics/impala_create_view.html">CREATE VIEW</a></li><li><a href="../topics/impala_delete.html">DELETE</a></li><li><a href="../topics/impala_describe.html">DESCRIBE</a></li><li><a href="../topics/impala_drop_database.html">DROP DATABASE</a></li><li><a href="../topics/impala_drop_function.html">DROP FUNCTION</a></li><li><a href="../topics/impala_drop_role.html">DROP ROLE</a></li><li><a href="../topics/impala_drop_stats.html">DROP STATS</a></li><li><a href="../topics/impala_drop_table.html">DROP TABLE</a></li><li><a href="../topics/impala_drop_view.html">DROP VIEW</a></li><li><a href="../topics/impala_explain.html">EXPLAIN</a></li><li><a href="../topics/impala_grant.html">GRANT</a></li><li><a href="../topics/impala_insert.html">INSERT</a></li><li><a href="../topics/impala_invalidate_metadata.html">INVALIDATE METADATA</a></li><li><a href="../topics/impala_load_data.html">LOAD DATA</a></li><li><a href="../topics/impala_refresh.html">REFRESH</a></li><li><a href="../topics/impala_refresh_authorization.html">REFRESH AUTHORIZATION</a></li><li><a href="../topics/impala_refresh_functions.html">REFRESH FUNCTIONS</a></li><li><a href="../topics/impala_revoke.html">REVOKE</a></li><li><a href="../topics/impala_select.html">SELECT</a></li><li><a href="../topics/impala_set.html">SET</a><ul><li><a href="../topics/impala_query_options.html">Query Options for the SET Statement</a><ul><li><a href="../topics/impala_abort_on_error.html">ABORT_ON_ERROR</a></li><li><a href="../topics/impala_allow_erasure_coded_files.html">ALLOW_ERASURE_CODED_FILES</a></li><li><a href="../topics/impala_allow_unsupported_formats.html">ALLOW_UNSUPPORTED_FORMATS</a></li><li><a href="../topics/impala_appx_count_distinct.html">APPX_COUNT_DISTINCT</a></li><li><a href="../topics/impala_batch_size.html">BATCH_SIZE</a></li><li><a href="../topics/impala_broadcast_bytes_limit.html">BROADCAST_BYTES_LIMIT</a></li><li><a href="../topics/impala_buffer_pool_limit.html">BUFFER_POOL_LIMIT</a></li><li><a href="../topics/impala_compression_codec.html">COMPRESSION_CODEC</a></li><li><a href="../topics/impala_compute_stats_min_sample_size.html">COMPUTE_STATS_MIN_SAMPLE_SIZE</a></li><li><a href="../topics/impala_debug_action.html">DEBUG_ACTION</a></li><li><a href="../topics/impala_decimal_v2.html">DECIMAL_V2</a></li><li><a href="../topics/impala_default_file_format.html">DEFAULT_FILE_FORMAT</a></li><li><a href="../topics/impala_default_hints_insert_statement.html">DEFAULT_HINTS_INSERT_STATEMENT</a></li><li><a href="../topics/impala_default_join_distribution_mode.html">DEFAULT_JOIN_DISTRIBUTION_MODE</a></li><li><a href="../topics/impala_default_spillable_buffer_size.html">DEFAULT_SPILLABLE_BUFFER_SIZE</a></li><li><a href="../topics/impala_default_transactional_type.html">DEFAULT_TRANSACTIONAL_TYPE</a></li><li><a href="../topics/impala_delete_stats_in_truncate.html">DELETE_STATS_IN_TRUNCATE</a></li><li><a href="../topics/impala_disable_codegen.html">DISABLE_CODEGEN</a></li><li><a href="../topics/impala_disable_codegen_rows_threshold.html">DISABLE_CODEGEN_ROWS_THRESHOLD</a></li><li class="active"><a href="../topics/impala_disable_hbase_num_rows_estimate.html">DISABLE_HBASE_NUM_ROWS_ESTIMATE</a></li><li><a href="../topics/impala_disable_row_runtime_filtering.html">DISABLE_ROW_RUNTIME_FILTERING</a></li><li><a href="../topics/impala_disable_streaming_preaggregations.html">DISABLE_STREAMING_PREAGGREGATIONS</a></li><li><a href="../topics/impala_disable_unsafe_spills.html">DISABLE_UNSAFE_SPILLS</a></li><li><a href="../topics/impala_enable_expr_rewrites.html">ENABLE_EXPR_REWRITES</a></li><li><a href="../topics/impala_exec_single_node_rows_threshold.html">EXEC_SINGLE_NODE_ROWS_THRESHOLD</a></li><li><a href="../topics/impala_exec_time_limit_s.html">EXEC_TIME_LIMIT_S</a></li><li><a href="../topics/impala_explain_level.html">EXPLAIN_LEVEL</a></li><li><a href="../topics/impala_fetch_rows_timeout_ms.html">FETCH_ROWS_TIMEOUT_MS</a></li><li><a href="../topics/impala_join_rows_produced_limit.html">JOIN_ROWS_PRODUCED_LIMIT</a></li><li><a href="../topics/impala_hbase_cache_blocks.html">HBASE_CACHE_BLOCKS</a></li><li><a href="../topics/impala_hbase_caching.html">HBASE_CACHING</a></li><li><a href="../topics/impala_idle_session_timeout.html">IDLE_SESSION_TIMEOUT</a></li><li><a href="../topics/impala_kudu_read_mode.html">KUDU_READ_MODE</a></li><li><a href="../topics/impala_live_progress.html">LIVE_PROGRESS</a></li><li><a href="../topics/impala_live_summary.html">LIVE_SUMMARY</a></li><li><a href="../topics/impala_max_errors.html">MAX_ERRORS</a></li><li><a href="../topics/impala_max_mem_estimate_for_admission.html">MAX_MEM_ESTIMATE_FOR_ADMISSION</a></li><li><a href="../topics/impala_max_result_spooling_mem.html">MAX_RESULT_SPOOLING_MEM</a></li><li><a href="../topics/impala_max_row_size.html">MAX_ROW_SIZE</a></li><li><a href="../topics/impala_max_scan_range_length.html">MAX_SCAN_RANGE_LENGTH</a></li><li><a href="../topics/impala_max_spilled_result_spooling_mem.html">MAX_SPILLED_RESULT_SPOOLING_MEM</a></li><li><a href="../topics/impala_mem_limit.html">MEM_LIMIT</a></li><li><a href="../topics/impala_min_spillable_buffer_size.html">MIN_SPILLABLE_BUFFER_SIZE</a></li><li><a href="../topics/impala_mt_dop.html">MT_DOP</a></li><li><a href="../topics/impala_num_nodes.html">NUM_NODES</a></li><li><a href="../topics/impala_num_rows_produced_limit.html">NUM_ROWS_PRODUCED_LIMIT</a></li><li><a href="../topics/impala_num_scanner_threads.html">NUM_SCANNER_THREADS</a></li><li><a href="../topics/impala_optimize_partition_key_scans.html">OPTIMIZE_PARTITION_KEY_SCANS</a></li><li><a href="../topics/impala_parquet_compression_codec.html">PARQUET_COMPRESSION_CODEC</a></li><li><a href="../topics/impala_parquet_annotate_strings_utf8.html">PARQUET_ANNOTATE_STRINGS_UTF8</a></li><li><a href="../topics/impala_parquet_array_resolution.html">PARQUET_ARRAY_RESOLUTION</a></li><li><a href="../topics/impala_parquet_dictionary_filtering.html">PARQUET_DICTIONARY_FILTERING</a></li><li><a href="../topics/impala_parquet_fallback_schema_resolution.html">PARQUET_FALLBACK_SCHEMA_RESOLUTION</a></li><li><a href="../topics/impala_parquet_file_size.html">PARQUET_FILE_SIZE</a></li><li><a href="../topics/impala_parquet_object_store_split_size.html">PARQUET_OBJECT_STORE_SPLIT_SIZE</a></li><li><a href="../topics/impala_parquet_page_row_count_limit.html">PARQUET_PAGE_ROW_COUNT_LIMIT</a></li><li><a href="../topics/impala_parquet_read_statistics.html">PARQUET_READ_STATISTICS</a></li><li><a href="../topics/impala_parquet_read_page_index.html">PARQUET_READ_PAGE_INDEX</a></li><li><a href="../topics/impala_parquet_write_page_index.html">PARQUET_WRITE_PAGE_INDEX</a></li><li><a href="../topics/impala_prefetch_mode.html">PREFETCH_MODE</a></li><li><a href="../topics/impala_query_timeout_s.html">QUERY_TIMEOUT_S</a></li><li><a href="../topics/impala_refresh_updated_hms.html">REFRESH_UPDATED_HMS_PARTITIONS</a></li><li><a href="../topics/impala_replica_preference.html">REPLICA_PREFERENCE</a></li><li><a href="../topics/impala_request_pool.html">REQUEST_POOL</a></li><li><a href="../topics/impala_resource_trace_ratio.html">RESOURCE_TRACE_RATIO</a></li><li><a href="../topics/impala_retry_failed_queries.html">RETRY_FAILED_QUERIES</a></li><li><a href="../topics/impala_runtime_bloom_filter_size.html">RUNTIME_BLOOM_FILTER_SIZE</a></li><li><a href="../topics/impala_runtime_filter_max_size.html">RUNTIME_FILTER_MAX_SIZE</a></li><li><a href="../topics/impala_runtime_filter_min_size.html">RUNTIME_FILTER_MIN_SIZE</a></li><li><a href="../topics/impala_runtime_filter_mode.html">RUNTIME_FILTER_MODE</a></li><li><a href="../topics/impala_runtime_filter_wait_time_ms.html">RUNTIME_FILTER_WAIT_TIME_MS</a></li><li><a href="../topics/impala_s3_skip_insert_staging.html">S3_SKIP_INSERT_STAGING</a></li><li><a href="../topics/impala_scan_bytes_limit.html">SCAN_BYTES_LIMIT</a></li><li><a href="../topics/impala_schedule_random_replica.html">SCHEDULE_RANDOM_REPLICA</a></li><li><a href="../topics/impala_scratch_limit.html">SCRATCH_LIMIT</a></li><li><a href="../topics/impala_shuffle_distinct_exprs.html">SHUFFLE_DISTINCT_EXPRS</a></li><li><a href="../topics/impala_spool_query_results.html">SPOOL_QUERY_RESULTS</a></li><li><a href="../topics/impala_support_start_over.html">SUPPORT_START_OVER</a></li><li><a href="../topics/impala_sync_ddl.html">SYNC_DDL</a></li><li><a href="../topics/impala_thread_reservation_aggregate_limit.html">THREAD_RESERVATION_AGGREGATE_LIMIT</a></li><li><a href="../topics/impala_thread_reservation_limit.html">THREAD_RESERVATION_LIMIT</a></li><li><a href="../topics/impala_timezone.html">TIMEZONE</a></li><li><a href="../topics/impala_topn_bytes_limit.html">TOPN_BYTES_LIMIT</a></li><li><a href="../topics/impala_utf8_mode.html">UTF8_MODE</a></li><li><a href="../topics/impala_expand_complex_types.html">EXPAND_COMPLEX_TYPES</a></li></ul></li></ul></li><li><a href="../topics/impala_show.html">SHOW</a></li><li><a href="../topics/impala_shutdown.html">SHUTDOWN</a></li><li><a href="../topics/impala_truncate_table.html">TRUNCATE TABLE</a></li><li><a href="../topics/impala_update.html">UPDATE</a></li><li><a href="../topics/impala_upsert.html">UPSERT</a></li><li><a href="../topics/impala_use.html">USE</a></li><li><a href="../topics/impala_values.html">VALUES</a></li><li><a href="../topics/impala_hints.html">Optimizer Hints</a></li></ul></li><li><a href="../topics/impala_functions.html">Built-In Functions</a></li><li><a href="../topics/impala_udf.html">User-Defined Functions (UDFs)</a></li><li><a href="../topics/impala_langref_unsupported.html">SQL Differences Between Impala and Hive</a></li><li><a href="../topics/impala_porting.html">Porting SQL</a></li><li><a href="../topics/impala_utf_8.html">UTF-8 Support</a></li></ul></li><li><a href="../topics/impala_performance.html">Performance Tuning</a></li><li><a href="../topics/impala_scalability.html">Scalability Considerations</a></li><li><a href="../topics/impala_resource_management.html">Resource Management</a></li><li><a href="../topics/impala_partitioning.html">Partitioning</a></li><li><a href="../topics/impala_file_formats.html">File Formats</a></li><li><a href="../topics/impala_kudu.html">Using Impala to Query Kudu Tables</a></li><li><a href="../topics/impala_hbase.html">HBase Tables</a></li><li><a href="../topics/impala_iceberg.html">Iceberg Tables</a></li><li><a href="../topics/impala_s3.html">S3 Tables</a></li><li><a href="../topics/impala_adls.html">ADLS Tables</a></li><li><a href="../topics/impala_isilon.html">Isilon Storage</a></li><li><a href="../topics/impala_ozone.html">Ozone Storage</a></li><li><a href="../topics/impala_logging.html">Logging</a></li><li><a href="../topics/impala_client.html">Client Access</a></li><li><a href="../topics/impala_fault_tolerance.html">Fault Tolerance</a></li><li><a href="../topics/impala_troubleshooting.html">Troubleshooting Impala</a></li><li><a href="../topics/impala_ports.html">Ports Used by Impala</a></li><li><a href="../topics/impala_reserved_words.html">Impala Reserved Words</a></li><li><a href="../topics/impala_faq.html">Impala Frequently Asked Questions</a></li><li><a href="../topics/impala_release_notes.html">Impala Release Notes</a></li></ul></nav><main role="main"><article role="article" aria-labelledby="ariaid-title1">
<h1 class="title topictitle1" id="ariaid-title1">DISABLE_HBASE_NUM_ROWS_ESTIMATE Query Option</h1>
<div class="body conbody">
<p class="p">
Use the <code class="ph codeph">DISABLE_HBASE_NUM_ROWS_ESTIMATE</code> query option to disable key
sampling of HBase tables in row count and row size estimation.
</p>
<p class="p">
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 <code class="ph codeph">DISABLE_HBASE_NUM_ROWS_ESTIMATE</code> query option
to <code class="ph codeph">TRUE</code>. And Impala planner will fall back to using Hive Metastore (HMS)
table stats instead.
</p>
<p class="p">
When <code class="ph codeph">DISABLE_HBASE_NUM_ROWS_ESTIMATE</code> query option is set to
<code class="ph codeph">TRUE</code>, you need to update the HMS table stats by running <code class="ph codeph">COMPUTE
STATS</code>. Alternatively, you can manually set table statistics by running
<code class="ph codeph">ALTER TABLE</code>. See <a class="xref" href="impala_perf_stats.html#perf_stats">Table and Column Statistics</a>
for details.
</p>
<div class="p">
The following values are supported:
<ul class="ul">
<li class="li">
<code class="ph codeph">TRUE</code> or <code class="ph codeph">1</code>: Disables the normal key sampling of HBase
tables and uses HMS table stats for estimation.
</li>
<li class="li">
<code class="ph codeph">FALSE</code> or <code class="ph codeph">0</code>: Enables the normal sampling of HBase
tables.
</li>
</ul>
</div>
<p class="p">
<strong class="ph b">Type:</strong> <code class="ph codeph">BOOLEAN</code>
</p>
<p class="p">
<strong class="ph b">Default:</strong> <code class="ph codeph">FALSE</code>
</p>
</div>
<nav role="navigation" class="related-links"><div class="familylinks"><div class="parentlink"><strong>Parent topic:</strong> <a class="link" href="../topics/impala_query_options.html">Query Options for the SET Statement</a></div></div></nav></article></main></body></html>