SOLR-12401: Add refGuide docs and CHANGES

solr/CHANGES.txt

@@ -143,6 +143,8 @@ New Features
 * SOLR-11453: Configuring slowQueryThresholdMillis logs slow requests to a separate file - solr_slow_requests.log .
   (Shawn Heisey, Remko Popma, Varun Thacker)
 
+* SOLR-12401: Add getValue() and setValue() Stream Evaluators (Joel Bernstein, janhoy) 
+
 * SOLR-11779: Basic long-term collection of aggregated metrics. Historical data is
   maintained as multi-resolution time series using round-robin databases in the '.system'
   collection. New /admin/metrics/history API allows retrieval of this data in numeric

solr/solr-ref-guide/src/stream-evaluator-reference.adoc

@@ -1018,6 +1018,23 @@ getRowLabels(matrix)
 
 string array: The labels for each row in the matrix
 
+== getValue
+
+The `getValue` function returns the value of a single Tuple entry by key.
+
+=== getValue Parameters
+
+* `tuple`: The Tuple to return the entry from.
+* `key`: The key of the entry to return the value for.
+
+=== getValue Syntax
+
+getValue(tuple, key)
+
+=== getValue Returns
+
+object: Returns an object of the same type as the Tuple entry.
+
 == grandSum
 
 The `grandSum` function sums all the values in a matrix.
@@ -2063,6 +2080,24 @@ setRowLabels(matrix, labels)
 
 matrix: The matrix with the labels set.
 
+== setValue
+
+The `setValue` function sets a new value for a Tuple entry.
+
+=== setValue Parameters
+
+* `tuple`: The Tuple to return the entry from.
+* `key`: The key of the entry to set.
+* `value`: The value to set.
+
+=== setValue Syntax
+
+setValue(tuple, key, value)
+
+=== setValue Returns
+
+tuple: Returns the new modified tuple
+
 == sin
 
 The `sin` function returns the trigonometric sine of a number.