Merge partition sections (#2165)

docs/developer-guide/partition-data.rst

@@ -11,8 +11,7 @@ Co-partitioning Requirements
 ****************************
 
 * The input records for the join must have the :ref:`same keying scheme <keys-have-same-keying-scheme>`
-  and the :ref:`same number of partitions <keys-have-same-number-of-partitions>` on both sides.
-* The key for the join must be in the :ref:`same partition <records-are-in-the-same-partition>` on both sides. 
+* The input records must have the :ref:`same number of partitions <keys-have-same-number-of-partitions>` on both sides.
 * Both sides of the join must have the :ref:`same partitioning strategy <records-have-same-partitioning-strategy>`.  
 
 When your inputs are co-partitioned, records with the same key, from both
@@ -22,8 +21,8 @@ them <ensure-co-partitioning>` by using the PARTITION BY clause.
 
 .. _keys-have-same-keying-scheme:
 
-Same Keying Scheme
-==================
+Records Have the Same Keying Scheme
+===================================
 
 The input records for the join must have the same keying scheme, which means
 that the join must use the same key field on both sides.
@@ -34,8 +33,8 @@ The join won't match if the key fields don't have the same name and type.
 
 .. _keys-have-same-number-of-partitions:
 
-Number of Partitions is Equal
-=============================
+Records Have the Same Number of Partitions
+==========================================
 
 The input records for the join must have the same number of partitions on both
 sides.
@@ -47,17 +46,6 @@ Use the ``<path-to-confluent>/bin/kafka-topics`` CLI tool
 with the ``--describe`` option to see the number of partitions for the
 Kafka topics that correspond with your streams and tables.
 
-.. _records-are-in-the-same-partition:
-
-Records Are In The Same Partition
-=================================
-
-The input records for the join must be in the same partition on both sides.
-
-For example, in a stream-table join, if a ``userId`` key with the value ``alice123``
-is in Partition 1 for the stream, but ``alice123`` is in Partition 2 for the table,
-the join won't match, even though both sides are keyed by ``userId``.
-
 .. _records-have-same-partitioning-strategy:
 
 Records Have the Same Partitioning Strategy
@@ -71,7 +59,13 @@ But if the producer applications for your records have custom partitioners
 specified in `configuration <http://kafka.apache.org/documentation/#producerconfigs>`__,
 the same custom partitioner logic must be used for records on both sides of the join.
 The applications that write to the join inputs must have the same partitioning
-strategy so that records with the same key are delivered to same partition number.
+strategy, so that records with the same key are delivered to same partition number.
+
+This means that the input records must be in the same partition on both sides
+of the join. For example, in a stream-table join, if a ``userId`` key with the
+value ``alice123`` is in Partition 1 for the stream, but ``alice123`` is in
+Partition 2 for the table, the join won't match, even though both sides are
+keyed by ``userId``.
 
 KSQL can't verify whether the partitioning strategies are the same for
 both join inputs, so you must ensure this.