Relation does not exist when configuring Mapnik with PostGIS table

Question

I am trying to create a Mapnik layer based on a PostGIS table, and I keep getting an error message when trying to load the layer

Postgis Plugin: ERROR: relation "public.myTable" does not exist ...

. This is my first time working with PostGIS and I've gotten Mapnik working with other layer types, but I was wanting to experiment with the possibility of using PostGIS.

I created the table I'm trying to use with QGIS, and I can see the table inside of QGIS in the database manager and through psql.

This is what my layer definition looks like in Mapnik

  <Layer name="myLayer" srs="+init=epsg:4326">
    <StyleName>My Style</StyleName>
    <Datasource>
      <Parameter name="type">postgis</Parameter>
      <Parameter name="host">localhost</Parameter>
      <Parameter name="dbname">postgis</Parameter>
      <Parameter name="user">postgres</Parameter>
      <Parameter name="password">[password]</Parameter>
      <Parameter name="table">public.myTable</Parameter>
      <Parameter name="estimate_extent">true</Parameter>
    </Datasource>
  </Layer>

I've tried "public.myTable", "public"."myTable", and myTable. I've tried uppercase, lowercase, and actual case.

Why is Mapnik failing to load this table?

Answer 1

I'm not sure what has changed, but apparently this was just a random transient problem... or I wasn't patient enough when trying different table names (it takes about 10 seconds for the map to render, and I may have jumped to the conclusion that it wasn't working before it had a chance to finish)

through my experimentation I have found the following

Values that do work

<Parameter name="table">"MyTable"</Parameter>

<Parameter name="table">"public"."MyTable"</Parameter>

Values that do not work

<Parameter name="table">MyTable</Parameter>

<Parameter name="table">public.MyTable</Parameter>

<Parameter name="table">"public.MyTable"</Parameter>

also I found that the table name is case sensitive, so any variation in capitalization of the values that do work like "Public"."MyTable" or "mytable", do not work.

After I got it to work with just the table name I tried doing a select statement on the table, and I found that quotes are necessary for column names as well, which is odd since that is not shown in the Mapnik documentation. I tried something similar to below

<Parameter name="table">(SELECT geom,someColumn from "public"."MyTable") as table</Parameter>

This did not work and instead I had to do the following

<Parameter name="table">(SELECT "geom","someColumn" from "public"."MyTable") as table</Parameter>