[couchdb-documentation] branch master updated: Document seq_interval parameter (#261)

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The following commit(s) were added to refs/heads/master by this push:
     new 87a4f3f  Document seq_interval parameter (#261)
87a4f3f is described below

commit 87a4f3f90867a39aef63c831368f5fccc5631001
Author: Juanjo Rodriguez <jj...@gmail.com>
AuthorDate: Mon Mar 19 00:45:19 2018 +0100

    Document seq_interval parameter (#261)
    
    * Document seq_interval parameter
---
 src/api/database/changes.rst | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/api/database/changes.rst b/src/api/database/changes.rst
index 41c581d..7bdfe11 100644
--- a/src/api/database/changes.rst
+++ b/src/api/database/changes.rst
@@ -102,6 +102,13 @@
         counted as "passed" for view filter in case if map function emits
         at least one record for them.
         See :ref:`changes/filter/view` for more info.
+    :query number seq_interval: When fetching changes in a batch, setting the
+        *seq_interval* parameter tells CouchDB to only calculate the update seq
+        with every Nth result returned. By setting **seq_interval=<batch size>**
+        , where ``<batch size>`` is the number of results requested per batch,
+        load can be reduced on the source CouchDB database; computing the seq
+        value across many shards (esp. in highly-sharded databases) is expensive
+        in a heavily loaded CouchDB cluster.
     :>header Cache-Control: ``no-cache`` if changes feed is
         :ref:`eventsource <changes/eventsource>`
     :>header Content-Type: - :mimetype:`application/json`
@@ -191,7 +198,8 @@
 .. versionchanged:: 1.4.0 Support ``Last-Event-ID`` header.
 .. versionchanged:: 1.6.0 added ``attachments`` and ``att_encoding_info``
    parameters
-.. versionchanged:: 2.0.0 update sequences can be any valid json object
+.. versionchanged:: 2.0.0 update sequences can be any valid json object,
+   added ``seq_interval``
 
 .. note::
     If the specified replicas of the shards in any given since value are
@@ -201,6 +209,13 @@
     of the `_changes` feed should be ‘idempotent’, that is, able to receive the
     same data multiple times, safely.
 
+.. note::
+    Cloudant Sync and PouchDB already optimize the replication process by
+    setting ``seq_interval`` parameter to the number of results expected per
+    batch. This parameter increases throughput by reducing latency between
+    sequential requests in bulk document transfers. This has resulted in up to
+    a 20% replication performance improvement in highly-sharded databases.
+
 .. warning::
     Using the ``attachments`` parameter to include attachments in the changes
     feed is not recommended for large attachment sizes. Also note that the

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