Some small tweaks to Red.

lib/MetamodelX/Red/Model.pm6

@@ -82,6 +82,10 @@ method columns(|) is rw {
     @!columns
 }
 
+method column-values (\model --> Hash) {
+    %(@!columns.map: { %!attr-to-column{.name} => .get_value(model) });
+}
+
 #| Returns a hash with the migration hash
 method migration-hash(\model --> Hash()) {
     columns => @!columns>>.column>>.migration-hash,
@@ -447,7 +451,12 @@ multi method create(\model, *%orig-pars, :$with where not .defined) is rw {
         my $filter = model.^id-filter: |do if $data.defined and not $data.elems {
             $*RED-DB.execute(Red::AST::LastInsertedRow.new: model).row{|@ids}:kv
         } else {
-            $data{|@ids}:kv
+            my %data-copy = model.^id>>.column.map({
+                $data{.name}:exists
+                    ?? (.attr-name => $data{.name})
+                    !! (.attr-name => $data{.attr-name})
+            });
+            %data-copy{|@ids}:kv
         }.Hash if @ids;
 
         for %positionals.kv -> $name, @val {

lib/Red/Driver/CommonSQL.pm6

@@ -523,7 +523,7 @@ multi method translate(Red::AST::Value $_ where .type ~~ Red::AST::Select, $cont
 }
 
 multi method translate(Red::AST::Value $_ where .type ~~ Positional, $context?) {
-    '( ' ~ .get-value.map( -> $v { '?' } ).join(', ') ~ ' )' => .get-value;
+    '( ' ~ .get-value.map( -> $v { self.wildcard } ).join(', ') ~ ' )' => .get-value;
 }
 
 multi method translate(Red::AST::Value $_ where .type.HOW ~~ Metamodel::EnumHOW, $context?) {
@@ -738,4 +738,4 @@ multi method prepare-json-path-item(@items) {
 }
 multi method prepare-json-path-item(Red::AST::Value $_) { self.prepare-json-path-item: .value }
 multi method prepare-json-path-item(Int $_) { "[{ $_ }]" }
-multi method prepare-json-path-item(Str $_) { ".{ $_ }"  }
+multi method prepare-json-path-item(Str $_) { ".{ $_ }"  }

lib/Red/Driver/Pg.pm6

@@ -115,6 +115,10 @@ multi method default-type-for(Red::Column $ where .attr.type ~~ Bool
 multi method default-type-for(Red::Column $ where .attr.type ~~ UUID                        --> Str:D) {"uuid"}
 multi method default-type-for(Red::Column $                                                 --> Str:D) {"varchar(255)"}
 
+multi method type-by-name("text" --> "text") {}
+multi method type-by-name("json" --> "json") {}
+multi method type-by-name("jsonb" --> "jsonb") {}
+
 multi method inflate(Str $value, DateTime :$to!) { DateTime.new: $value }
 
 multi method map-exception(DB::Pg::Error::FatalError $x where .?message ~~ /"duplicate key value violates unique constraint " \"$<field>=(\w+)\"/) {

t/20-in-pg.t

@@ -0,0 +1,48 @@
+use Red;
+use Test;
+
+my $*RED-PG-TEST-DB = $_ with %*ENV<RED_PG_TEST_DB>;
+
+my $*RED-DEBUG          = $_ with %*ENV<RED_DEBUG>;
+my $*RED-DEBUG-AST      = $_ with %*ENV<RED_DEBUG_AST>;
+
+plan 2;
+unless $*RED-PG-TEST-DB {
+    "No RED_PG_TEST_DB initialized.".say;
+    skip-rest 2;
+}
+
+model Category is table<test_category> {
+    has Int $.id is serial;
+    has Int $.parent_id is column{ :references{ Category.id }, :nullable, };
+    has Str $.name is column;
+
+    has Category $.parent is relationship{ .parent_id };
+    has Category @.children is relationship{ .parent_id };
+}
+
+$GLOBAL::RED-DB = database "Pg", :dbname($*RED-PG-TEST-DB);
+
+Category.^create-table;
+
+my $parent = Category.^create: :name('xx');
+
+for [1 .. 5] -> $x {
+    Category.^create: :parent_id($parent.id), :name("child-$x");
+}
+
+# # This worked.
+# (Category.^rs.grep: { .id (<) Category.^all.grep({ .id == 3 }).map({ .id }) } ).Seq.perl.say;
+
+# # This doesn't.
+# (Category.^rs.grep: { .id (<) $parent.children.map({ .id }) } ).Seq.perl.say;
+
+
+
+# This worked in SQLite (But doesn't work with Pg driver.)
+# my $*RED-DEBUG-AST = True;
+my @seq = $parent.children.map({ .id }).Seq.sort;
+
+is-deeply @seq, [Category.^rs.grep({ .id in @seq }).map(*.id).Seq.sort], "in with literal list for pg";
+is-deeply @seq, [Category.^rs.grep({ .id (<) @seq }).map(*.id).Seq.sort], "in with literal list for pg (<) operator";
+