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ntimofeev pushed a commit to branch STABLE-4.1
in repository https://gitbox.apache.org/repos/asf/cayenne.git
commit 0808b2eb0762b67250b1ea4757d76f7c1e044e51
Author: Nikita Timofeev <stari...@gmail.com>
AuthorDate: Wed Jul 22 12:36:01 2020 +0300
A note on MySQL JDBC driver and iterated queries
---
.../src/docs/asciidoc/_cayenne-guide/part2/tuning.adoc | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git
a/docs/asciidoc/cayenne-guide/src/docs/asciidoc/_cayenne-guide/part2/tuning.adoc
b/docs/asciidoc/cayenne-guide/src/docs/asciidoc/_cayenne-guide/part2/tuning.adoc
index 4b6da82..b8f24bd 100644
---
a/docs/asciidoc/cayenne-guide/src/docs/asciidoc/_cayenne-guide/part2/tuning.adoc
+++
b/docs/asciidoc/cayenne-guide/src/docs/asciidoc/_cayenne-guide/part2/tuning.adoc
@@ -234,6 +234,23 @@ try(ResultBatchIterator<Artist> it =
ObjectSelect.query(Artist.class).batchItera
}
----
+===== MySQL JDBC driver and iterated queries
+
+The MySQL JDBC driver is known to pull the entire ResultSet into memory.
+In order to get the driver to stream the results, append the JDBC parameter
+`useCursorFetch=true` to the JDBC URL.
+
+A fetch size must also be set when doing the query using
+`ObjectSelect.statementFetchSize(..)`, for example:
+[source, java]
+----
+ObjectSelect.query(queryClass)
+ .statementFetchSize(50000)
+ .iterate(objectContext, cayenneObject -> ...
+----
+Adjust the value of the fetch size to fit requirements. A larger value is more
+performant, but consumes more memory as well.
+
==== Paginated Queries
Enabling query pagination allows to load very large result sets in a Java app
with very little memory overhead
