OPENJPA-2555 add docs for DateFractionDigits
diff --git a/openjpa-project/src/doc/manual/ref_guide_dbsetup.xml b/openjpa-project/src/doc/manual/ref_guide_dbsetup.xml
index a021dc0..6de9dac 100644
--- a/openjpa-project/src/doc/manual/ref_guide_dbsetup.xml
+++ b/openjpa-project/src/doc/manual/ref_guide_dbsetup.xml
@@ -1423,6 +1423,27 @@
Defaults to <literal>"CURRENT_TIMESTAMP"</literal>.
</para>
</listitem>
+ <listitem id="DBDictionary.DateFractionDigits">
+ <para>
+ <indexterm>
+ <primary>
+ JDBC
+ </primary>
+ <secondary>
+ DateFractionDigits
+ </secondary>
+ </indexterm>
+ <literal>DateFractionDigits</literal>
+ Some databases support to store sub-second fraction values.
+ The digits to store can sometimes be configured.
+ This value defines the default number of digits to store in the database.
+ A <code>dateFractionDigits=3</code> will e.g. lead to a <code>DATETIME(3)</code> on some databases.
+
+ Note that this default can be overwritten to an integer value n per column via
+ <code>@Column(scale=n)</code>.
+ A <code>@Column(scale=-1)</code> will set the fraction digits to zero.
+ </para>
+ </listitem>
<listitem id="DBDictionary.DatePrecision">
<para>
<indexterm>
@@ -3897,6 +3918,26 @@
properties:
</para>
<itemizedlist>
+ <listitem id="MySQLDictionary.DateFractionDigits">
+ <para>
+ <indexterm>
+ <primary>
+ MySQL
+ </primary>
+ <secondary>
+ DateFractionDigits
+ </secondary>
+ </indexterm>
+ <literal>DateFractionDigits</literal>:
+ Since MySQL 5.8 a timestamp (<code>DATETIME</code>) can store up to 6 sub-second fractions.
+ The default in MySQL and OpenJPA is 0 for backward compatibility reasons.
+ This default can be changed by setting <literal>DateFractionDigits</literal> to the number of
+ sub-second fraction digits to be stored. This will e.g. result in a <code>DATETIME(6)</code> column.
+ The number of fraction digits to be generated can also be tweaked via the
+ <code>@Column(scale=n)</code> annotation, where n is the number of digits.
+ This setting has primarily an impact on the generated SQL.
+ </para>
+ </listitem>
<listitem id="MySQLDictionary.DriverDeserializesBlobs">
<para>
<indexterm>
