Types of Indexes - Apache Drill

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class="toctree-l2"><a class="reference internal" href="/docs/analyzing-highly-dynamic-datasets/">Analyzing Highly Dynamic Datasets</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/analyzing-social-media/">Analyzing Social Media</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/analyzing-data-using-window-functions/">Analyzing Data Using Window Functions</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/orchestrating-queries-with-airflow/">Orchestrating queries with Airflow</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Drill-on-YARN</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/drill-on-yarn-introduction/">Drill-on-YARN Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/creating-a-basic-drill-cluster/">Creating a Basic Drill Cluster</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/launch-drill-under-yarn/">Launch Drill Under YARN</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/configuration-reference/">Configuration Reference</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/drill-on-yarn-command-line-tool/">Drill-on-YARN Command-Line Tool</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/using-the-drill-on-yarn-web-ui/">Using the Drill-on-YARN Web UI</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/multiple-drill-clusters/">Multiple Drill Clusters</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/enabling-web-ui-security/">Enabling Web UI Security</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/appendix-a-release-note-issues/">Appendix A: Release Note Issues</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/appendix-b-drill-env-sh-settings/">Appendix B: drill-env.sh Settings</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/appendix-c-troubleshooting/">Appendix C: Troubleshooting</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/appendix-d-recreate-the-drill-archive/">Appendix D: Recreate the Drill Archive</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Install Drill</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/install-drill-introduction/">Install Drill Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/migrating-parquet-data/">Migrating Parquet Data</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Installing Drill in Embedded Mode</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/embedded-mode-prerequisites/">Embedded Mode Prerequisites</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/running-drill-on-docker/">Running Drill on Docker</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/installing-drill-on-linux-and-mac-os-x/">Installing Drill on Linux and Mac OS X</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/starting-drill-on-linux-and-mac-os-x/">Starting Drill on Linux and Mac OS X</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/installing-drill-on-windows/">Installing Drill on Windows</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/starting-drill-on-windows/">Starting Drill on Windows</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Installing Drill in Distributed Mode</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/distributed-mode-prerequisites/">Distributed Mode Prerequisites</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/installing-drill-on-the-cluster/">Installing Drill on the Cluster</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/starting-drill-in-distributed-mode/">Starting Drill in Distributed Mode</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/starting-the-web-ui/">Starting the Web UI</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/stopping-drill/">Stopping Drill</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/identifying-multiple-drill-versions-in-a-cluster/">Identifying Multiple Drill Versions in a Cluster</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Extended</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/installing-drill-in-distributed-mode-with-gcp-dataproc/">Installing Drill in Distributed Mode with GCP Dataproc</a></li> </ul> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Configure Drill</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/configure-drill-introduction/">Configure Drill Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/configuring-drill-memory/">Configuring Drill Memory</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Securing Drill</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/securing-drill-introduction/">Securing Drill Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/secure-communication-paths/">Secure Communication Paths</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/roles-and-privileges/">Roles and Privileges</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-user-impersonation/">Configuring User Impersonation</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-inbound-impersonation/">Configuring Inbound Impersonation</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-user-impersonation-with-hive-authorization/">Configuring User Impersonation with Hive Authorization</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-user-security/">Configuring User Security</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-plain-security/">Configuring Plain Security</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-ssl-tls-for-encryption/">Configuring SSL/TLS for Encryption</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-libpam4j-as-the-pam-authenticator/">Using libpam4j as the PAM Authenticator</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-jpam-as-the-pam-authenticator/">Using jpam as the PAM Authenticator</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-htpasswd-file-authentication/">Configuring htpasswd file authentication</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-hashicorp-vault-authentication/">Configuring HashiCorp Vault authentication</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-kerberos-security/">Configuring Kerberos Security</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-drill-to-use-spnego-for-http-authentication/">Configuring Drill to use SPNEGO for HTTP Authentication</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-web-ui-and-rest-api-security/">Configuring Web UI and REST API Security</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-custom-acls-to-secure-znodes/">Configuring Custom ACLs to Secure znodes</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Configuring a Multitenant Cluster</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-a-multitenant-cluster-introduction/">Configuring a Multitenant Cluster Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-multitenant-resources/">Configuring Multitenant Resources</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-resources-for-a-shared-drillbit/">Configuring Resources for a Shared Drillbit</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Configuration Options</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/configuration-options-introduction/">Configuration Options Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/start-up-options/">Start-Up Options</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/planning-and-execution-options/">Planning and Execution Options</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/persistent-configuration-storage/">Persistent Configuration Storage</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/global-query-list/">Global Query List</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/ports-and-bind-addresses-used-by-drill/">Ports and Bind Addresses Used by Drill</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/configuring-the-drill-shell/">Configuring the Drill Shell</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/configuring-cgroups-to-control-cpu-usage/">Configuring cgroups to Control CPU Usage</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Connect a Data Source</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/connect-a-data-source-introduction/">Connect a Data Source Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/storage-plugin-registration/">Storage Plugin Registration</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Storage Plugin Configuration</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/plugin-configuration-basics/">Plugin Configuration Basics</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-storage-plugins/">Configuring Storage Plugins</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/storage-plugin-authentication-modes/">Storage plugin authentication modes</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/workspaces/">Workspaces</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/drill-default-input-format/">Drill Default Input Format</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/file-system-storage-plugin/">File System Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/hbase-storage-plugin/">HBase Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/hive-storage-plugin/">Hive Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/rdbms-storage-plugin/">RDBMS Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/mongodb-storage-plugin/">MongoDB Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/mapr-db-format/">MapR-DB Format</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/s3-storage-plugin/">S3 Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/oci-os-storage-plugin/">OCI OS Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/opentsdb-storage-plugin/">OpenTSDB Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/kafka-storage-plugin/">Kafka Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/azure-blob-storage-plugin/">Azure Blob Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/druid-storage-plugin/">Druid Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/http-storage-plugin/">HTTP Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/elasticsearch-storage-plugin/">ElasticSearch Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/splunk-storage-plugin/">Splunk Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/cassandra-storage-plugin/">Cassandra Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/dropbox-storage-plugin/">Dropbox Storage Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/google-sheets-storage-plugin/">Google Sheets Storage Plugin</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">ODBC/JDBC Interfaces</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/interfaces-introduction/">Interfaces Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/using-the-jdbc-driver/">Using the JDBC Driver</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/using-jdbc-with-squirrel-on-windows/">Using JDBC with SQuirreL on Windows</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Installing the ODBC Driver</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/installing-the-driver-on-linux/">Installing the Driver on Linux</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/installing-the-driver-on-mac-os-x/">Installing the Driver on Mac OS X</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/installing-the-driver-on-windows/">Installing the Driver on Windows</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Configuring ODBC</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/odbc-configuration-reference/">ODBC Configuration Reference</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/logging-and-tracing/">Logging and Tracing</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-odbc-on-linux/">Configuring ODBC on Linux</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-odbc-on-mac-os-x/">Configuring ODBC on Mac OS X</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-odbc-on-windows/">Configuring ODBC on Windows</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/testing-the-odbc-connection/">Testing the ODBC Connection</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Using Drill Explorer</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/drill-explorer-introduction/">Drill Explorer Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/connecting-drill-explorer-to-data/">Connecting Drill Explorer to Data</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/browsing-data-and-defining-views/">Browsing Data and Defining Views</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Using Drill with BI Tools</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/using-drill-with-bi-tools-introduction/">Using Drill with BI Tools Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/tableau-examples/">Tableau Examples</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-microstrategy-analytics-with-apache-drill/">Using MicroStrategy Analytics with Apache Drill</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-tibco-spotfire-desktop-with-drill/">Using Tibco Spotfire Desktop with Drill</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-tibco-spotfire-server-with-drill/">Configuring Tibco Spotfire Server with Drill</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-qlik-sense-with-drill/">Using Qlik Sense with Drill</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-apache-drill-with-tableau-10-2/">Using Apache Drill with Tableau 10.2</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-apache-drill-with-tableau-9-desktop/">Using Apache Drill with Tableau 9 Desktop</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-apache-drill-with-tableau-9-server/">Using Apache Drill with Tableau 9 Server</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-information-builders-webfocus-with-apache-drill/">Using Information Builders’ WebFOCUS with Apache Drill</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-jreport-with-drill/">Configuring JReport with Drill</a></li> </ul> </ul> <li class="toctree-l1 current_section "><a href="javascript: void(0);">Query Data</a></li> <ul class="current_section"> <li class="toctree-l2"><a class="reference internal" href="/docs/query-data-introduction/">Query Data Introduction</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Querying a File System</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-a-file-system-introduction/">Querying a File System Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-avro-files/">Querying Avro Files</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-json-files/">Querying JSON Files</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-parquet-files/">Querying Parquet Files</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-plain-text-files/">Querying Plain Text Files</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-directories/">Querying Directories</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-sequence-files/">Querying Sequence Files</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/querying-hbase/">Querying HBase</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Querying Complex Data</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-complex-data-introduction/">Querying Complex Data Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/sample-data-donuts/">Sample Data: Donuts</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/selecting-flat-data/">Selecting Flat Data</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/using-sql-functions-clauses-and-joins/">Using SQL Functions, Clauses, and Joins</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/selecting-nested-data-for-a-column/">Selecting Nested Data for a Column</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/selecting-multiple-columns-within-nested-data/">Selecting Multiple Columns Within Nested Data</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/querying-hive/">Querying Hive</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/querying-the-information-schema/">Querying the INFORMATION SCHEMA</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Querying Indexes</a></li> <ul style=""> <li class="toctree-l3"><a class="reference internal" href="/docs/querying-indexes-introduction/">Querying Indexes Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/queries-that-qualify-for-index-based-query-plans/">Queries that Qualify for Index-Based Query Plans</a></li> <li class="toctree-l3 current"><a class="reference internal" href="/docs/types-of-indexes/">Types of Indexes</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/index-selection/">Index Selection</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/designing-indexes-for-your-queries/">Designing Indexes for Your Queries</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/configuring-index-planning/">Configuring Index Planning</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/verifying-index-use/">Verifying Index Use</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/querying-system-tables/">Querying System Tables</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/monitoring-and-canceling-queries-in-the-drill-web-ui/">Monitoring and Canceling Queries in the Drill Web UI</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Performance Tuning</a></li> <ul style="display: none"> <li class="toctree-l2"><a href="javascript: void(0);">Drill Metastore</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/using-drill-metastore/">Using Drill Metastore</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/drill-iceberg-metastore/">Drill Iceberg Metastore</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/rdbms-metastore/">RDBMS Metastore</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/mongo-metastore/">Mongo Metastore</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/performance-tuning-introduction/">Performance Tuning Introduction</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Partition Pruning</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/partition-pruning-introduction/">Partition Pruning Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/how-to-partition-data/">How to Partition Data</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/asynchronous-parquet-reader/">Asynchronous Parquet Reader</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/optimizing-parquet-metadata-reading/">Optimizing Parquet Metadata Reading</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/parquet-filter-pushdown/">Parquet Filter Pushdown</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/hive-metadata-caching/">Hive Metadata Caching</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/choosing-a-storage-format/">Choosing a Storage Format</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Query Plans and Tuning</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/query-plans-and-tuning-introduction/">Query Plans and Tuning Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/join-planning-guidelines/">Join Planning Guidelines</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/guidelines-for-optimizing-aggregation/">Guidelines for Optimizing Aggregation</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/modifying-query-planning-options/">Modifying Query Planning Options</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/sort-based-and-hash-based-memory-constrained-operators/">Sort-Based and Hash-Based Memory-Constrained Operators</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/enabling-query-queuing/">Enabling Query Queuing</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/throttling/">Throttling</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/controlling-parallelization-to-balance-performance-with-multi-tenancy/">Controlling Parallelization to Balance Performance with Multi-Tenancy</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Identifying Performance Issues</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/query-plans/">Query Plans</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/query-profiles/">Query Profiles</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Performance Tuning Reference</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/query-profile-column-descriptions/">Query Profile Column Descriptions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/physical-operators/">Physical Operators</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/monitoring-metrics/">Monitoring Metrics</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Log and Debug</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/log-and-debug-introduction/">Log and Debug Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/error-messages/">Error Messages</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/modify-logback-xml/">Modify logback.xml</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/review-the-java-stack-trace/">Review the Java Stack Trace</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/query-audit-logging/">Query Audit Logging</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">SQL Reference</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/sql-reference-introduction/">SQL Reference Introduction</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Data Types</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/supported-data-types/">Supported Data Types</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/date-time-and-timestamp/">Date, Time, and Timestamp</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/handling-different-data-types/">Handling Different Data Types</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/lexical-structure/">Lexical Structure</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/operators/">Operators</a></li> <li class="toctree-l2"><a href="javascript: void(0);">SQL Functions</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/about-sql-function-examples/">About SQL Function Examples</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/math-and-trig/">Math and Trig</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/statistical/">Statistical</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/data-type-conversion/">Data Type Conversion</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/data-type-functions/">Data Type Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/date-time-functions-and-arithmetic/">Date/Time Functions and Arithmetic</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/string-manipulation/">String Manipulation</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/aggregate-and-aggregate-statistical/">Aggregate and Aggregate Statistical</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/functions-for-handling-nulls/">Functions for Handling Nulls</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/phonetic-functions/">Phonetic Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/string-distance-functions/">String Distance Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/cryptography-functions/">Cryptography Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/sql-dialect-compatibility-functions/">SQL dialect compatibility functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/gis-functions/">GIS functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/time-series-analysis-functions/">Time Series Analysis Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/ip-networking-functions/">IP Networking functions</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">SQL Window Functions</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/sql-window-functions-introduction/">SQL Window Functions Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/aggregate-window-functions/">Aggregate Window Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/ranking-window-functions/">Ranking Window Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/value-window-functions/">Value Window Functions</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/sql-window-functions-examples/">SQL Window Functions Examples</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Nested Data Functions</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/nested-data-limitations/">Nested Data Limitations</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/flatten/">FLATTEN</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/kvgen/">KVGEN</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/repeated-count/">REPEATED_COUNT</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/repeated-contains/">REPEATED_CONTAINS</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/list-creation-functions/">COLLECT_LIST</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/query-directory-functions/">Query Directory Functions</a></li> <li class="toctree-l2"><a href="javascript: void(0);">SQL Commands</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/supported-sql-commands/">Supported SQL Commands</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/analyze-table-refresh-metadata/">ANALYZE TABLE REFRESH METADATA</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/analyze-table-compute-statistics/">ANALYZE TABLE COMPUTE STATISTICS</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/set/">SET</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/refresh-table-metadata/">REFRESH TABLE METADATA</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/reset/">RESET</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/alter-system/">ALTER SYSTEM</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/create-or-replace-schema/">CREATE OR REPLACE SCHEMA</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/create-table-as-ctas/">CREATE TABLE AS (CTAS)</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/create-temporary-table-as-cttas/">CREATE TEMPORARY TABLE AS (CTTAS)</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/create-function-using-jar/">CREATE FUNCTION USING JAR</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/partition-by-clause/">PARTITION BY Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/create-view/">CREATE VIEW</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/describe/">DESCRIBE</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/drop-function-using-jar/">DROP FUNCTION USING JAR</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/drop-table/">DROP TABLE</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/drop-view/">DROP VIEW</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/explain/">EXPLAIN</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/lateral-join/">LATERAL Join</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/select/">SELECT</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/select-list/">SELECT List</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/from-clause/">FROM Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/group-by-clause/">GROUP BY Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/having-clause/">HAVING Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/limit-clause/">LIMIT Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/offset-clause/">OFFSET Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/order-by-clause/">ORDER BY Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/set-operators/">Set Operators</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/where-clause/">WHERE Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/with-clause/">WITH Clause</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/show-databases-and-show-schemas/">SHOW DATABASES and SHOW SCHEMAS</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/show-files/">SHOW FILES</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/show-tables/">SHOW TABLES</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/use/">USE</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/pivot-operators/">Pivot Operators</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">SQL Conditional Expressions</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/case/">CASE</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/reserved-keywords/">Reserved Keywords</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/sql-extensions/">SQL Extensions</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Data Sources and File Formats</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/data-sources-and-file-formats-introduction/">Data Sources and File Formats Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/hive-to-drill-data-type-mapping/">Hive-to-Drill Data Type Mapping</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/deploying-and-using-a-hive-udf/">Deploying and Using a Hive UDF</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/parquet-format/">Parquet Format</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/logfile-plugin/">Logfile Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/json-data-model/">JSON Data Model</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/text-files-csv-tsv-psv/">Text Files: CSV, TSV, PSV</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/sequence-files/">Sequence Files</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/httpd-format-plugin/">HTTPD Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/image-metadata-format-plugin/">Image Metadata Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/syslog-format-plugin/">Syslog Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/ltsv-format-plugin/">LTSV Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/spss-format-plugin/">SPSS Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/esri-shapefile-format-plugin/">ESRI Shapefile Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/excel-format-plugin/">Excel Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/hdf5-format-plugin/">HDF5 Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/ms-access-format-plugin/">Microsoft Access Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/xml-format-plugin/">XML Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/iceberg-format-plugin/">Iceberg Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/delta-lake-format-plugin/">Delta Lake Format Plugin</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/sas-format-plugin/">SAS Format Plugin</a></li> </ul> <li class="toctree-l1"><a href="javascript: void(0);">Develop Custom Functions</a></li> <ul style="display: none"> <li class="toctree-l2"><a class="reference internal" href="/docs/develop-custom-functions-introduction/">Develop Custom Functions Introduction</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/developing-a-simple-function/">Developing a Simple Function</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/tutorial-develop-a-simple-function/">Tutorial: Develop a Simple Function</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/developing-an-aggregate-function/">Developing an Aggregate Function</a></li> <li class="toctree-l2"><a href="javascript: void(0);">Adding Custom Functions to Drill</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/adding-custom-functions-to-drill-introduction/">Adding Custom Functions to Drill Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/manually-adding-custom-functions-to-drill/">Manually Adding Custom Functions to Drill</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/creating-custom-authenticators/">Creating Custom Authenticators</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/dynamic-udfs/">Dynamic UDFs</a></li> </ul> <li class="toctree-l2"><a class="reference internal" href="/docs/using-custom-functions-in-queries/">Using Custom Functions in Queries</a></li> <li class="toctree-l2"><a class="reference internal" href="/docs/custom-function-interfaces/">Custom Function Interfaces</a></li> </ul> <li class="toctree-l1"><a class="reference internal" href="/docs/troubleshooting/">Troubleshooting</a></li> <li class="toctree-l1"><a href="javascript: void(0);">Developer Information</a></li> <ul style="display: none"> <li class="toctree-l2"><a href="javascript: void(0);">REST API</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/rest-api-introduction/">REST API Introduction</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/submitting-queries-from-the-rest-api-when-impersonation-is-enabled-and-authentication-is-disabled/">Submitting Queries from the REST API when Impersonation is Enabled and Authentication is Disabled</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/use-postman-to-run-sql-queries-on-drill-data-sources/">Use Postman to Run SQL Queries on Drill Data Sources</a></li> </ul> <li class="toctree-l2"><a href="javascript: void(0);">Develop Drill</a></li> <ul style="display: none"> <li class="toctree-l3"><a class="reference internal" href="/docs/compiling-drill-from-source/">Compiling Drill from Source</a></li> <li class="toctree-l3"><a class="reference internal" href="/docs/useful-information-for-drill-developers/">Useful Information for Drill Developers</a></li> </ul> <li class="toctree-l2"><a href="javascript: 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class="main-content-wrapper"> <div class="main-content"> <a class="edit-link" href="https://github.com/apache/drill-site/blob/master/_docs/en/query-data/querying-indexes/021-types-of-indexes.md" target="_blank"><i class="fa fa-pencil-square-o"></i></a> <div class="int_title left"> <h1>Types of Indexes</h1> </div>  <div class="int_text" align="left"> <p>The query planner in Drill can leverage indexes to create index-based query plans for improved query performance. An index is either covering or non-covering based on the columns referenced in the query and the columns in the index. Indexes for queries with ORDER BY may be hashed or non-hashed, affecting the sort order of the indexes. Drill also supports indexes on the CAST function.</p> <p>The following sections describe these indexes in more detail and show examples of query plans generated for each.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Currently, Drill works with the types of indexes supported by MapR Database. The following sections demonstrate how Drill works with indexes in the MapR Database. </p> </div> <h2 id="covering-index">Covering Index</h2> <p>A covering index is an index that “covers” all the columns referenced in a query. Only the index is needed to process the query. Covering indexes avoid the overhead of fetching data from the primary table. A covering index can include indexed and non-indexed (included) columns.</p> <p>For example, suppose an index is created and queried, as follows:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>index keys:{a}, included columns: {b} and the query is SELECT a, b FROM T WHERE a > 10 AND b < 20. </code></pre></div></div> <p>Since columns a, b are present in the index, this is a covering index. The Drill planner generates a covering index plan (index-only plan) where all the columns are retrieved from the index after pushing down relevant filter conditions to the index scan.</p> <h3 id="covering-index-example">Covering Index Example</h3> <p>This example uses an index, l_comp_1, created on a table named lineitem with indexed columns L_LINENUMBER and L_ORDERKEY and also includes columns L_LINESTATUS and L_QUANTITY.</p> <p>The following query references the L_LINESTATUS, L_QUANTITY, L_LINENUMBER, and L_ORDERKEY columns in the lineitem table:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>SELECT L_LINESTATUS, L_QUANTITY FROM lineitem WHERE L_LINENUMBER = 1 AND L_ORDERKEY BETWEEN 40 AND 75; </code></pre></div></div> <p>Because the l_comp_1 index includes all columns referenced in the query, the query planner in Drill creates a covering index plan.</p> <p>Running the EXPLAIN PLAN FOR command with the query shows that Drill created a query plan that only uses the index to process the query:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>EXPLAIN PLAN FOR SELECT L_LINESTATUS, L_QUANTITY FROM lineitem WHERE L_LINENUMBER = 1 AND L_ORDERKEY BETWEEN 40 AND 75; 00-00 Screen 00-01 Project(L_LINESTATUS=[$0], L_QUANTITY=[$1]) 00-02 Scan(table=[[si, tpch_sf1_maprdb_range, lineitem]], groupscan=[JsonTableGroupScan [ScanSpec=JsonScanSpec [tableName=maprfs:///drill/testdata/tpch/sf1/maprdb/json/range/lineitem, condition=(((L_LINENUMBER = {"$numberLong":1}) and (L_ORDERKEY >= {"$numberLong":40})) and (L_ORDERKEY <= {"$numberLong":75})), indexName=l_comp_1], columns=[`L_LINESTATUS`, `L_QUANTITY`]]]) </code></pre></div></div> <p>Reading the query plan, you can see that the plan includes an index scan, as indicated by <code class="language-plaintext highlighter-rouge">groupscan=[JsonTableGroupScan</code> and <code class="language-plaintext highlighter-rouge">indexName=l_comp_1</code>. Drill and the data source can process this query using only the index.</p> <h2 id="non-covering-index">Non-Covering Index</h2> <p>A non-covering index is an index that does not “cover” all the columns referenced in a query. A non-covering index has indexed and/or non-indexed (included) columns that only partially cover the columns referenced in a query. A non-covering query plan includes an index scan and a join back to the primary table. In some scenarios, a full table scan is more cost efficient than an index scan and Drill will not create an index-based query plan.</p> <p>For example, suppose an index is created and queried, as follows:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>index keys:{a, b}, included columns: {c} and the query is SELECT d, e FROM T WHERE a > 10 AND b < 20. </code></pre></div></div> <p>Since columns d, e are not present in the index, this is a non-covering index. For such indexes, the Drill planner generates a non-covering index plan where only the row ids are fetched from the index by pushing down the WHERE clause filters and the rest of the columns are fetched after a join-back to the primary table. The join-back is performed using the row ids.</p> <h3 id="non-covering-index-example">Non-Covering Index Example</h3> <p>This example uses an index, l_comp_1, created on a table named lineitem with indexed columns L_LINENUMBER and L_ORDERKEY and also included columns L_LINESTATUS and L_QUANTITY.</p> <p>The following query references the L_RETURNFLAG, L_LINESTATUS, L_QUANTITY L_LINENUMBER, and L_ORDERKEY columns in the lineitem table:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>SELECT L_RETURNFLAG, L_LINESTATUS, L_QUANTITY FROM lineitem WHERE L_LINENUMBER = 1 AND L_ORDERKEY BETWEEN 40 AND 75; </code></pre></div></div> <p>Because the l_comp_1 index does not include the L_RETURNFLAG column, the query planner in Drill creates a non-covering index plan that uses the index, but also includes a join on the primary table.</p> <p>Running the EXPLAIN PLAN FOR command with the query shows that Drill includes an index scan and a table scan with a rowkey join:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>EXPLAIN PLAN FOR SELECT L_RETURNFLAG, L_LINESTATUS, L_QUANTITY FROM lineitem WHERE L_LINENUMBER = 1 AND L_ORDERKEY BETWEEN 40 AND 75; 00-00 Screen 00-01 Project(L_RETURNFLAG=[$0], L_LINESTATUS=[$1], L_QUANTITY=[$2]) 00-02 Project(L_RETURNFLAG=[$2], L_LINESTATUS=[$3], L_QUANTITY=[$4]) 00-03 Project(L_LINENUMBER=[$0], L_ORDERKEY=[$1], L_RETURNFLAG=[$2], L_LINESTATUS=[$3], L_QUANTITY=[$4]) 00-04 RowKeyJoin(condition=[=($5, $6)], joinType=[inner]) 00-06 Scan(table=[[si, tpch_sf1_maprdb_range, lineitem]], groupscan=[RestrictedJsonTableGroupScan [ScanSpec=JsonScanSpec [tableName=maprfs:///drill/testdata/tpch/sf1/maprdb/json/range/lineitem, condition=(((L_LINENUMBER = {"$numberLong":1}) and (L_ORDERKEY >= {"$numberLong":40})) and (L_ORDERKEY <= {"$numberLong":75}))], columns=[`L_LINENUMBER`, `L_ORDERKEY`, `L_RETURNFLAG`, `L_LINESTATUS`, `L_QUANTITY`, `_id`], rowcount=60012.15000000001]]) 00-05 Scan(table=[[si, tpch_sf1_maprdb_range, lineitem]], groupscan=[JsonTableGroupScan [ScanSpec=JsonScanSpec [tableName=maprfs:///drill/testdata/tpch/sf1/maprdb/json/range/lineitem, condition=(((L_LINENUMBER = {"$numberLong":1}) and (L_ORDERKEY >= {"$numberLong":40})) and (L_ORDERKEY <= {"$numberLong":75})), indexName=l_comp_1], columns=[`_id`]]]) </code></pre></div></div> <p>Reading the non-covering index plan, you can see that the plan includes an index scan, as indicated by the <code class="language-plaintext highlighter-rouge">groupscan=[JsonTableGroupScan</code> and <code class="language-plaintext highlighter-rouge">indexName=l_comp_1</code>, and also a scan on the primary table, as indicated by the <code class="language-plaintext highlighter-rouge">groupscan=[RestrictedJsonTableGroupScan</code> and the <code class="language-plaintext highlighter-rouge">RowKeyJoin</code>. To process this query, Drill can use the index with the data source, but the data source must also use the rowkey join on the primary table to fetch data in the L_RETURNFLAG column. Note that this is not a real join, but more of a lookup based on the rowid. This is a random I/O operation from the primary table since each row id may access a separate data block from the table.</p> <p>If this query ran on a regular basis, you could remove the l_comp_1 index and create a new index that includes all columns referenced in the query, including the L_RETURNFLAG column, to improve query performance. However, running a query only once or a few times may not justify the overhead of removing the old index and creating a new index.</p> <h2 id="non-hashed-indexes">Non-Hashed Indexes</h2> <p>Non-hashed indexes support conditional queries with an ORDER BY clause. When processing ORDER BY queries, Drill does not have to perform sort operations on the data.</p> <h3 id="non-hashed-index-plan-example">Non-Hashed Index Plan Example</h3> <p>A non-hashed index, l_comp_1, was created on a table, lineitem with indexed columns L_LINENUMBER and L_ORDERKEY and included columns L_LINESTATUSand L_QUANTITY.</p> <p>Running the example query with the EXPLAIN PLAN FOR command shows that Drill produces an index plan without the additional sort and merge operations when using the non-hashed index to process the query, as follows:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>EXPLAIN PLAN FOR SELECT L_LINESTATUS, L_QUANTITY FROM lineitem WHERE L_LINENUMBER = 1 AND L_ORDERKEY BETWEEN 40 AND 75 ORDER BY L_LINENUMBER; 00-00 Screen 00-01 Project(L_LINESTATUS=[$0], L_QUANTITY=[$1]) 00-02 Project(L_LINESTATUS=[$2], L_QUANTITY=[$3], L_LINENUMBER=[$0]) 00-03 Scan(table=[[si, tpch_sf1_maprdb_range, lineitem]], groupscan=[JsonTableGroupScan [ScanSpec=JsonScanSpec [tableName=maprfs:///drill/testdata/tpch/sf1/maprdb/json/range/lineitem, condition=(((L_LINENUMBER = {"$numberLong":1}) and (L_ORDERKEY >= {"$numberLong":40})) and (L_ORDERKEY <= {"$numberLong":75})), indexName=l_comp_1], columns=[`L_LINENUMBER`, `L_ORDERKEY`, `L_LINESTATUS`, `L_QUANTITY`]]]) </code></pre></div></div> <p>Reading the query plan, you can see that Drill uses the non-hashed index plan, as indicated by <code class="language-plaintext highlighter-rouge">indexName=l_comp_1</code>. To process the query, the data source uses the index and Drill does not have to perform sort and merge operations on the data, as indicated by the absence of the Sort and SingleMergeExchange operations in the query plan. The data source sorted the data in the index when the index was created.</p> <h2 id="hashed-indexes">Hashed Indexes</h2> <p>Hashed indexes support the same conditional queries as non-hashed indexes, but they do not have a guaranteed sort order. Hashed indexes enable the data source to evenly distribute new writes on an index across logical partitions to avoid hot spotting. Drill must perform a sort for ORDER BY queries that use hashed indexes. Sorting the data can increase the CPU costs and negatively impact performance.</p> <p>If you notice performance issues with ORDER BY queries that use hashed indexes, review the query plans to see if the plans include sort and merge operations. If this is the case, create non-hashed indexes to support the queries and achieve the best performance.</p> <h3 id="hashed-index-plan-example">Hashed Index Plan Example</h3> <p>A hashed index, l_hash_comp_1, was created with indexed columns L_LINENUMBER and L_ORDERKEY and included columns L_LINESTATUS and L_QUANTITY.</p> <p>Running the example query with the EXPLAIN PLAN FOR command shows that Drill produces an index plan with sort and merge operations to process the query when using the hashed index, as follows:</p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>EXPLAIN PLAN FOR SELECT L_LINESTATUS, L_QUANTITY FROM lineitem WHERE L_LINENUMBER = 1 AND L_ORDERKEY BETWEEN 40 AND 75 ORDER BY L_LINENUMBER; 00-00 Screen 00-01 Project(L_LINESTATUS=[$0], L_QUANTITY=[$1]) 00-02 SingleMergeExchange(sort0=[2]) 01-01 SelectionVectorRemover 01-02 Sort(sort0=[$2], dir0=[ASC]) 01-03 Project(L_LINESTATUS=[$2], L_QUANTITY=[$3], L_LINENUMBER=[$0]) 01-04 Scan(table=[[si, tpch_sf1_maprdb_hash, lineitem]], groupscan=[JsonTableGroupScan [ScanSpec=JsonScanSpec [tableName=maprfs:///drill/testdata/tpch/sf1/maprdb/json/hash/lineitem, condition=(((L_LINENUMBER = {"$numberLong":1}) and (L_ORDERKEY >= {"$numberLong":40})) and (L_ORDERKEY <= {"$numberLong":75})), indexName=l_hash_comp_1], columns=[`L_LINENUMBER`, `L_ORDERKEY`, `L_LINESTATUS`, `L_QUANTITY`]]]) </code></pre></div></div> <p>Reading the query plan, you can see that Drill uses the hashed index in the plan, as indicated by <code class="language-plaintext highlighter-rouge">indexName=l_hash_comp_1</code>. To process the query, the data source can use the index, but Drill must sort and merge the data, as indicated by the <code class="language-plaintext highlighter-rouge">Sort</code> and <code class="language-plaintext highlighter-rouge">SingleMergeExchange</code> operations in the query plan. Using the hashed index plan for this ORDER BY query requires additional processing and negatively impacts performance.</p> <h2 id="functional-index">Functional Index</h2> <p>A functional index is an index created on functions or expressions instead of columns in a table. CAST functions are most commonly used in Drill views. For example, if the filter condition is ‘WHERE CAST(zip_code as BIGINT) = 95120’ and a functional index exists on CAST(zip_code as BIGINT), the query planner will leverage the index.</p> <p>When issuing Drill queries through BI tools, you can include CAST functions in your queries to create <a href="/docs/create-view/">Drill views</a>. Including CAST functions provides the metadata needed to optimally process the queries. For more information about using the CAST function with Drill, see <a href="/docs/data-type-conversion/">Data Type Conversion</a>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">MapR Database supports functional indexes. 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Types of Indexes - Apache Drill