What is an Elasticsearch / Apache Solr index ? For dummies

622 views September 27, 2016 December 15, 2017 admin 1

wpsolr Elasticsearch / Apache solr index database mapping

An Elasticsearch / Apache Solr index is the equivalent of a SQL table.

An Elasticsearch or Solr server (aka Solr instance, aka Solr engine) can maintain several indexes.


Each index contains types, defined with a mapping. The index type mapping is equivalent to a SQL table schema definition.

Apache Solr

Each index is defined by a schema.xml file (it’s not mandatory in Solr 5/6, but recommended in production), and a solrconfig.xml file. The index schema is equivalent to a SQL table schema definition.


An index contains several documents, equivalent to SQL table rows. Each document contains fields, equivalent to SQL table columns.

When an index document is inserted/updated/deleted, we say it is “indexed”.

To retrieve documents from an index, Elasticsearch (json) / Apache Solr (xml, json) provide an http API, with a proprietary syntax.

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