Docs: Fix description, value range, and defaults for optimizer_nestloop_factor
<topic id="optimizer_nestloop_factor">
<title>optimizer_nestloop_factor</title>
<body>
- <p>When GPORCA is enabled (the default), this parameter controls the nested loop join cost
- factor to apply to during query optimization. The default value, <codeph>1</codeph>,
- specifies the default sort cost factor. The value is a ratio of increase or decrease from
- the default factor. For example, a value of <codeph>2.0</codeph> sets the cost factor at
- twice the default, and a value of <codeph>0.5</codeph> sets the factor at half the
- default.</p>
+ <p>This parameter adds a costing factor to GPORCA to prioritize hash joins instead of nested
+ loop joins during query optimization. The default value of 1024 was chosen after evaluating
+ numerous workloads with uniformly distributed data. 1024 should be treated as the practical
+ upper bound setting for this parameter. If you find the GPORCA selects hash joins more often
+ than it should, reduce the value to shift the costing factor in favor of nested loop
+ joins.</p>
<p>The parameter can be set for a database system, an individual database, or a session or
query.</p>
<table id="table_zy2_xlj_tz">
</thead>
<tbody>
<row>
- <entry colname="col1">Decimal > 0</entry>
- <entry colname="col2">1</entry>
+ <entry colname="col1">INT_MAX > 1</entry>
+ <entry colname="col2">1024</entry>
<entry colname="col3">master<p>session</p><p>reload</p></entry>
</row>
</tbody>
