Some small tweaks to Red.

lib/MetamodelX/Red/Model.pm6

@@ -81,6 +81,10 @@ 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,

lib/Red/Driver/Pg.pm6

@@ -34,6 +34,22 @@ multi method translate(Red::AST::Select $_, $context?, :$gambi where !*.defined)
     self.Red::Driver::CommonSQL::translate($_, $context, :gambi);
 }
 
+multi method translate(Red::AST::In $_, $context?) {
+    if .right.value ~~ Positional {
+        my ($lstr, @lbind) := do given self.translate: .left,  $context { .key, .value }
+
+        if .right.value.elems == 0 {
+            return "$lstr { .op } (SELECT 0 WHERE false)" => @lbind;
+        }
+
+        my $in-placeholder = '(' ~ (self.wildcard xx .right.value.elems).join(',') ~ ')';
+
+        return "$lstr { .op } $in-placeholder" => [|@lbind, |.right.value];
+    } else {
+        nextsame;
+    }
+}
+
 multi method translate(Red::AST::RowId $_, $context?) { "OID" => [] }
 
 multi method translate(Red::AST::Delete $_, $context?, :$gambi where !*.defined) {
@@ -111,6 +127,10 @@ 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";
+