readyset-server: Check that placeholders' columns exist

Migration was not checking that the column connected to a placeholder
actually existed, and most confusingly, migration would even succeed!
We only hit a problem when querying the resultant cache, which wouldn't
work and would return an error that didn't make sense.  We now try to
check whether the column exists.

Release-Note-Core: Check whether placeholders' columns (`zzz = $1`)
  exist during migration, and if not, report query as unsupported.
Fixes: REA-5454
Change-Id: I33fa590bb51b19bc0355ebf13c042dcbebaf2a4c
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/9022
Tested-by: Buildkite CI
Reviewed-by: Michael Zink <michael.z@readyset.io>

Author: rs-sac

readyset-server/src/controller/sql/query_graph.rs

@@ -1234,6 +1234,25 @@ pub fn to_query_graph(stmt: SelectStatement) -> ReadySetResult<QueryGraph> {
             // we also separately register it as a parameter so that we can set keys
             // correctly on the leaf view
             rel.parameters.push(param.clone());
+        } else {
+            let found = stmt.fields.iter().any(|f| {
+                matches!(
+                    f,
+                    FieldDefinitionExpr::Expr {
+                        alias: None,
+                        expr: Expr::Column(Column { name, .. }),
+                    }
+                    | FieldDefinitionExpr::Expr {
+                        alias: Some(name), ..
+                    } if *name == param.col.name
+                )
+            });
+            if !found {
+                unsupported!(
+                    "Column `{}` as placeholder cannot be resolved",
+                    param.col.name
+                );
+            }
         }
     }