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sql_query_range
Range query setup.
Optional, default is empty.
Applies to SQL source types (mysql, pgsql, mssql) only.
Setting this option enables ranged document fetch queries (see the section called “Ranged queries”). Ranged queries are useful to avoid notorious MyISAM table locks when indexing lots of data. (They also help with other less notorious issues, such as reduced performance caused by big result sets, or additional resources consumed by InnoDB to serialize big read transactions.)
The query specified in this option must fetch min and max document IDs that will be used as range boundaries. It must return exactly two integer fields, min ID first and max ID second; the field names are ignored.
When ranged queries are enabled, sql_query
will be required to contain $start and $end macros
(because it obviously would be a mistake to index the whole table many times over).
Note that the intervals specified by $start..$end
will not overlap, so you should not remove document IDs that are
exactly equal to $start or $end from your query.
The example in the section called “Ranged queries”) illustrates that; note how it
uses greater-or-equal and less-or-equal comparisons.
Example:
sql_query_range = SELECT MIN(id),MAX(id) FROM documents
