SLD ignoring PropertyName's case or using if_then_else

Question

I have Geoserver 2.19.1, using layers from both Postgres and Oracle, in two different workspaces. Most of the layers are based on identicaly described tables (same fields+datatypes, different content) on both sides, so I have e.g. the layer sdo_test.parcels (oracle) and pg_test.parcels (postgres).
The SLDs that decorate the layers are based on combinations of field (PropertyName) values. I want to use the same SLDs for both layers (many layers, fairly complex), but the obvious problem is that a field name (PropertyName, not referring to its content) is uppercase in oracle and lowercase in postgres.
I have tried the following in a simple SLD, but it does not validate, with Unable to find function if_then_else:

<?xml version="1.0" encoding="UTF-8"?>  
<StyledLayerDescriptor version="1.0.0" xmlns="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd">  
  <NamedLayer>
  <Name>gr16_subilotsXtra_style</Name>
  <UserStyle>
    <Title>gr16_subilotsXtra_style</Title>
      <FeatureTypeStyle>
        <Rule><Name>   </Name>
          <PolygonSymbolizer>
            <Fill><CssParameter name="fill"><ogc:Literal>#330000</ogc:Literal></CssParameter>
             <CssParameter name="fill-opacity"><ogc:Literal>0.69</ogc:Literal></CssParameter>
               </Fill>
            <Stroke><CssParameter name="stroke"><ogc:Literal>#330000</ogc:Literal></CssParameter>
             <CssParameter name="stroke-opacity"><ogc:Literal>1</ogc:Literal></CssParameter>
             <CssParameter name="stroke-width"><ogc:Literal>2</ogc:Literal></CssParameter>
               </Stroke>
          </PolygonSymbolizer>
          <TextSymbolizer>


                <Label>
              <!-- <ogc:PropertyName>SRC_ID</ogc:PropertyName> - this is the original setting-->

              <!-- and this is what I tried:-->
              <ogc:Function name="if_then_else">
                  <ogc:Function name="PropertyExists">
                      <ogc:PropertyName>src_id</ogc:PropertyName>
                  </ogc:Function>
                      <ogc:PropertyName>src_id</ogc:PropertyName>
              <ogc:Function name="if_then_else">
                  <ogc:Function name="PropertyExists">
                      <ogc:PropertyName>SRC_ID</ogc:PropertyName>
                  </ogc:Function>
                      <ogc:PropertyName>SRC_ID</ogc:PropertyName>
                  </ogc:Function>
              </ogc:Function>
              <!-- end of trying -->

            </Label>
            

                <Font><CssParameter name="font-size">12</CssParameter></Font>
            <Halo>
                <Radius>1</Radius>
                <Fill><CssParameter name="fill">#FFFFFF</CssParameter></Fill>
                 </Halo>
            <Fill><CssParameter name="fill">#000000</CssParameter></Fill>
          <VendorOption name="polygonAlign">mbr</VendorOption>

          </TextSymbolizer>
        </Rule>
      </FeatureTypeStyle>
  </UserStyle>

Answer 1

I thought you could do something like:

         <ogc:Function name="if_then_else">
            <ogc:Function name="PropertyExists">
              <ogc:PropertyName>state_abbr</ogc:PropertyName>
            </ogc:Function>
            <ogc:PropertyName>state_abbr</ogc:PropertyName>
            <ogc:PropertyName>STATE_ABBR</ogc:PropertyName>
          </ogc:Function>

but this fails to render as the attribute state_abbr doesn't exist in the layer. So I don't think this approach will work, all I can think of is fixing the attribute names or creating views on one or the other database.