Read documents from index (all or with filter)

Returns documents from an index (or alias) by using the index name as the table name. For server-side filtering use the Query parameter in the WITH clause; WHERE runs client-side and is slower.

Standard SQL query example

This is the base query accepted by the connector. To execute it in SQL Server, you have to pass it to the Data Gateway via a Linked Server. See how to accomplish this using the examples below.

SELECT * FROM MyIndexOrAliasName --WITH(Query='{"match": { "PartNumber" : "P50" } }')

Using OPENQUERY in SQL Server

SELECT * FROM OPENQUERY([LS_TO_ELASTICSEARCH_IN_GATEWAY], 'SELECT * FROM MyIndexOrAliasName --WITH(Query=''{"match": { "PartNumber" : "P50" } }'')')

Using EXEC in SQL Server (handling larger SQL text)

The major drawback of OPENQUERY is its inability to incorporate variables within SQL statements. This often leads to the use of cumbersome dynamic SQL (with numerous ticks and escape characters).

Fortunately, starting with SQL 2005 and onwards, you can utilize the EXEC (your_sql) AT [LS_TO_ELASTICSEARCH_IN_GATEWAY] syntax.

DECLARE @MyQuery NVARCHAR(MAX) = 'SELECT * FROM MyIndexOrAliasName --WITH(Query=''{"match": { "PartNumber" : "P50" } }'')'
EXEC (@MyQuery) AT [LS_TO_ELASTICSEARCH_IN_GATEWAY]