PostgreSQL MSI ignores --datadir flag during minor upgrade on Windows - Mailing list pgsql-bugs

Hello,

Recently we tried to upgrade a client machine's PostgreSQL version from 15.13 to 15.16.

We often upgrade our client machines from versions 9/13 to 15 without encountering any issues.

However, during this upgrade (15.13 --> 15.16) we've noticed that post-upgrade the PostgreSQL service assigned data directory changed to the default value "C:\Program Files\PostgreSQL\15\data".

Our client's data directory prior to the upgrade was "F:\AidocData\PostgreSQL\15\data". This change caused data to be written to the wrong location until we found the issue.

This is the command we use for the upgrade:

In server/pgserver.xml.in, in the server component’s preInstallationActionList:

pgserver.xml.in
Lines 1142-1153

        <!-- Set datadir if an existing installation is found -->
        <setInstallerVariable>
            <name>datadir</name>
            <value>${iDataDirectory}</value>
            <ruleList>
                <stringTest>
                    <text>${iDataDirectory}</text>
                    <type>not_empty</type>
                </stringTest>
                <isFalse value="${extract_mode}"/>
            </ruleList>
        </setInstallerVariable>

iDataDirectory is read from the registry here:
pgserver.xml.in
Lines 1003-1008

                <!-- Get the existing data directory. -->
                <registryGet>
                    <name>Data Directory</name>
                    <key>HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql${service_suffix}-${product_version}</key>
                    <variable>iDataDirectory</variable>
                </registryGet>

What goes wrong:
When passing --datadir "F:\AidocData\PostgreSQL\15\data" on the command line, the wizard sets datadir = "F:\AidocData\PostgreSQL\15\data".

Later, in preInstallationActionList, the installer reads iDataDirectory from the registry.
If iDataDirectory is not empty, it overwrites datadir with that value.

If the registry still has the old default path (e.g. C:\Program Files\PostgreSQL\15\data), the service ends up re-registered with that path instead of F:\AidocData\PostgreSQL\15\data.
When the registry can be wrong

Fix
Only use the registry value when the user has not provided --datadir on the command line. For example, add a condition so that datadir is set from iDataDirectory only when datadir is empty:

<!-- Set datadir if an existing installation is found (only when user didn't provide --datadir) -->
<setInstallerVariable>
    <name>datadir</name>
    <value>${iDataDirectory}</value>
    <ruleList>
        <stringTest>
            <text>${iDataDirectory}</text>
            <type>not_empty</type>
        </stringTest>
        <stringTest>
            <text>${datadir}</text>
            <type>empty</type>
        </stringTest>
        <isFalse value="${extract_mode}"/>
    </ruleList>
</setInstallerVariable>

This keeps the current behavior when --datadir is not passed, but ensures that an explicit --datadir is not overridden by the registry.