X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FStorage%2FDBIHacks.pm;h=b0dfe434a65e2c0fa09b185726ae1e602ade466c;hb=71b788fb0a6ec693cb27c44e326f01a219caf1a4;hp=3c7d1c43eeea969e62fb5f9bf2f42359b65f34d9;hpb=ad1d374e603e34f4f58d1004d0bf4e2b9982422d;p=dbsrgits%2FDBIx-Class.git

diff --git a/lib/DBIx/Class/Storage/DBIHacks.pm b/lib/DBIx/Class/Storage/DBIHacks.pm
index 3c7d1c4..b0dfe43 100644
--- a/lib/DBIx/Class/Storage/DBIHacks.pm
+++ b/lib/DBIx/Class/Storage/DBIHacks.pm
@@ -15,7 +15,9 @@ use mro 'c3';
 
 use List::Util 'first';
 use Scalar::Util 'blessed';
-use Sub::Name 'subname';
+use DBIx::Class::_Util qw(UNRESOLVABLE_CONDITION serialize);
+use SQL::Abstract qw(is_plain_value is_literal_value);
+use DBIx::Class::Carp;
 use namespace::clean;
 
 #
@@ -110,8 +112,8 @@ sub _adjust_select_args_for_complex_prefetch {
   my $outer_attrs = { %$attrs };
   delete @{$outer_attrs}{qw(from bind rows offset group_by _grouped_by_distinct having)};
 
-  my $inner_attrs = { %$attrs };
-  delete @{$inner_attrs}{qw(for collapse select as _related_results_construction)};
+  my $inner_attrs = { %$attrs, _simple_passthrough_construction => 1 };
+  delete @{$inner_attrs}{qw(for collapse select as)};
 
   # there is no point of ordering the insides if there is no limit
   delete $inner_attrs->{order_by} if (
@@ -415,7 +417,7 @@ sub _resolve_aliastypes_from_select_args {
   # generate sql chunks
   my $to_scan = {
     restricting => [
-      $sql_maker->_recurse_where ($attrs->{where}),
+      ($sql_maker->_recurse_where ($attrs->{where}))[0],
       $sql_maker->_parse_rs_attrs ({ having => $attrs->{having} }),
     ],
     grouping => [
@@ -428,46 +430,40 @@ sub _resolve_aliastypes_from_select_args {
       ),
     ],
     selecting => [
-      map { ($sql_maker->_recurse_fields($_))[0] } @{$attrs->{select}},
+      # kill all selectors which look like a proper subquery
+      # this is a sucky heuristic *BUT* - if we get it wrong the query will simply
+      # fail to run, so we are relatively safe
+      grep
+        { $_ !~ / \A \s* \( \s* SELECT \s+ .+? \s+ FROM \s+ .+? \) \s* \z /xsi }
+        map
+          { ($sql_maker->_recurse_fields($_))[0] }
+          @{$attrs->{select}}
     ],
     ordering => [
       map { $_->[0] } $self->_extract_order_criteria ($attrs->{order_by}, $sql_maker),
     ],
   };
 
-  # throw away empty chunks and all 2-value arrayrefs: the thinking is that these are
-  # bind value specs left in by the sloppy renderer above. It is ok to do this
-  # at this point, since we are going to end up rewriting this crap anyway
-  for my $v (values %$to_scan) {
-    my @nv;
-    for (@$v) {
-      next if (
-        ! defined $_
-          or
-        (
-          ref $_ eq 'ARRAY'
-            and
-          ( @$_ == 0 or @$_ == 2 )
-        )
-      );
+  # throw away empty-string chunks, and make sure no binds snuck in
+  # note that we operate over @{$to_scan->{$type}}, hence the
+  # semi-mindbending ... map ... for values ...
+  ( $_ = [ map {
 
-      if (ref $_) {
-        require Data::Dumper::Concise;
-        $self->throw_exception("Unexpected ref in scan-plan: " . Data::Dumper::Concise::Dumper($v) );
-      }
+      (not $_)        ? ()
+    : (length ref $_) ? (require Data::Dumper::Concise && $self->throw_exception(
+                          "Unexpected ref in scan-plan: " . Data::Dumper::Concise::Dumper($_)
+                        ))
+    :                   $_
 
-      push @nv, $_;
-    }
+  } @$_ ] ) for values %$to_scan;
 
-    $v = \@nv;
-  }
+  # throw away empty to-scan's
+  (
+    @{$to_scan->{$_}}
+      or
+    delete $to_scan->{$_}
+  ) for keys %$to_scan;
 
-  # kill all selectors which look like a proper subquery
-  # this is a sucky heuristic *BUT* - if we get it wrong the query will simply
-  # fail to run, so we are relatively safe
-  $to_scan->{selecting} = [ grep {
-    $_ !~ / \A \s* \( \s* SELECT \s+ .+? \s+ FROM \s+ .+? \) \s* \z /xsi
-  } @{ $to_scan->{selecting} || [] } ];
 
   # first see if we have any exact matches (qualified or unqualified)
   for my $type (keys %$to_scan) {
@@ -653,9 +649,10 @@ sub _group_over_selection {
   }
 
   $self->throw_exception ( sprintf
-    'A required group_by clause could not be constructed automatically due to a complex '
-  . 'order_by criteria (%s). Either order_by columns only (no functions) or construct a suitable '
-  . 'group_by by hand',
+    'Unable to programatically derive a required group_by from the supplied '
+  . 'order_by criteria. To proceed either add an explicit group_by, or '
+  . 'simplify your order_by to only include plain columns '
+  . '(supplied order_by: %s)',
     join ', ', map { "'$_'" } @$leftovers,
   ) if $leftovers;
 
@@ -709,6 +706,9 @@ sub _resolve_ident_sources {
 # for all sources
 sub _resolve_column_info {
   my ($self, $ident, $colnames) = @_;
+
+  return {} if $colnames and ! @$colnames;
+
   my $alias2src = $self->_resolve_ident_sources($ident);
 
   my (%seen_cols, @auto_colnames);
@@ -779,31 +779,9 @@ sub _resolve_column_info {
 sub _inner_join_to_node {
   my ($self, $from, $alias) = @_;
 
-  # subqueries and other oddness are naturally not supported
-  return $from if (
-    ref $from ne 'ARRAY'
-      ||
-    @$from <= 1
-      ||
-    ref $from->[0] ne 'HASH'
-      ||
-    ! $from->[0]{-alias}
-      ||
-    $from->[0]{-alias} eq $alias  # this last bit means $alias is the head of $from - nothing to do
-  );
-
-  # find the current $alias in the $from structure
-  my $switch_branch;
-  JOINSCAN:
-  for my $j (@{$from}[1 .. $#$from]) {
-    if ($j->[0]{-alias} eq $alias) {
-      $switch_branch = $j->[0]{-join_path};
-      last JOINSCAN;
-    }
-  }
+  my $switch_branch = $self->_find_join_path_to_node($from, $alias);
 
-  # something else went quite wrong
-  return $from unless $switch_branch;
+  return $from unless @{$switch_branch||[]};
 
   # So it looks like we will have to switch some stuff around.
   # local() is useless here as we will be leaving the scope
@@ -831,6 +809,29 @@ sub _inner_join_to_node {
   return \@new_from;
 }
 
+sub _find_join_path_to_node {
+  my ($self, $from, $target_alias) = @_;
+
+  # subqueries and other oddness are naturally not supported
+  return undef if (
+    ref $from ne 'ARRAY'
+      ||
+    ref $from->[0] ne 'HASH'
+      ||
+    ! defined $from->[0]{-alias}
+  );
+
+  # no path - the head is the alias
+  return [] if $from->[0]{-alias} eq $target_alias;
+
+  for my $i (1 .. $#$from) {
+    return $from->[$i][0]{-join_path} if ( ($from->[$i][0]{-alias}||'') eq $target_alias );
+  }
+
+  # something else went quite wrong
+  return undef;
+}
+
 sub _extract_order_criteria {
   my ($self, $order_by, $sql_maker) = @_;
 
@@ -880,15 +881,15 @@ sub _order_by_is_stable {
   my ($self, $ident, $order_by, $where) = @_;
 
   my @cols = (
-    (map { $_->[0] } $self->_extract_order_criteria($order_by)),
-    $where ? @{$self->_extract_fixed_condition_columns($where)} :(),
-  ) or return undef;
+    ( map { $_->[0] } $self->_extract_order_criteria($order_by) ),
+    ( $where ? keys %{ $self->_extract_fixed_condition_columns($where) } : () ),
+  ) or return 0;
 
   my $colinfo = $self->_resolve_column_info($ident, \@cols);
 
   return keys %$colinfo
     ? $self->_columns_comprise_identifying_set( $colinfo,  \@cols )
-    : undef
+    : 0
   ;
 }
 
@@ -904,115 +905,499 @@ sub _columns_comprise_identifying_set {
     return 1 if $src->_identifying_column_set($_);
   }
 
-  return undef;
+  return 0;
 }
 
-# this is almost identical to the above, except it accepts only
+# this is almost similar to _order_by_is_stable, except it takes
 # a single rsrc, and will succeed only if the first portion of the order
 # by is stable.
 # returns that portion as a colinfo hashref on success
-sub _main_source_order_by_portion_is_stable {
-  my ($self, $main_rsrc, $order_by, $where) = @_;
+sub _extract_colinfo_of_stable_main_source_order_by_portion {
+  my ($self, $attrs) = @_;
+
+  my $nodes = $self->_find_join_path_to_node($attrs->{from}, $attrs->{alias});
 
-  die "Huh... I expect a blessed result_source..."
-    if ref($main_rsrc) eq 'ARRAY';
+  return unless defined $nodes;
 
   my @ord_cols = map
     { $_->[0] }
-    ( $self->_extract_order_criteria($order_by) )
+    ( $self->_extract_order_criteria($attrs->{order_by}) )
   ;
   return unless @ord_cols;
 
-  my $colinfos = $self->_resolve_column_info($main_rsrc);
+  my $valid_aliases = { map { $_ => 1 } (
+    $attrs->{from}[0]{-alias},
+    map { values %$_ } @$nodes,
+  ) };
+
+  my $colinfos = $self->_resolve_column_info($attrs->{from});
+
+  my ($colinfos_to_return, $seen_main_src_cols);
+
+  for my $col (@ord_cols) {
+    # if order criteria is unresolvable - there is nothing we can do
+    my $colinfo = $colinfos->{$col} or last;
+
+    # if we reached the end of the allowed aliases - also nothing we can do
+    last unless $valid_aliases->{$colinfo->{-source_alias}};
+
+    $colinfos_to_return->{$col} = $colinfo;
+
+    $seen_main_src_cols->{$colinfo->{-colname}} = 1
+      if $colinfo->{-source_alias} eq $attrs->{alias};
+  }
+
+  # FIXME the condition may be singling out things on its own, so we
+  # conceivable could come back wi "stable-ordered by nothing"
+  # not confient enough in the parser yet, so punt for the time being
+  return unless $seen_main_src_cols;
+
+  my $main_src_fixed_cols_from_cond = [ $attrs->{where}
+    ? (
+      map
+      {
+        ( $colinfos->{$_} and $colinfos->{$_}{-source_alias} eq $attrs->{alias} )
+          ? $colinfos->{$_}{-colname}
+          : ()
+      }
+      keys %{ $self->_extract_fixed_condition_columns($attrs->{where}) }
+    )
+    : ()
+  ];
+
+  return $attrs->{result_source}->_identifying_column_set([
+    keys %$seen_main_src_cols,
+    @$main_src_fixed_cols_from_cond,
+  ]) ? $colinfos_to_return : ();
+}
+
+# Attempts to flatten a passed in SQLA condition as much as possible towards
+# a plain hashref, *without* altering its semantics. Required by
+# create/populate being able to extract definitive conditions from preexisting
+# resultset {where} stacks
+#
+# FIXME - while relatively robust, this is still imperfect, one of the first
+# things to tackle with DQ
+sub _collapse_cond {
+  my ($self, $where, $where_is_anded_array) = @_;
+
+  my $fin;
+
+  if (! $where) {
+    return;
+  }
+  elsif ($where_is_anded_array or ref $where eq 'HASH') {
+
+    my @pairs;
+
+    my @pieces = $where_is_anded_array ? @$where : $where;
+    while (@pieces) {
+      my $chunk = shift @pieces;
+
+      if (ref $chunk eq 'HASH') {
+        for (sort keys %$chunk) {
+
+          # Match SQLA 1.79 behavior
+          if ($_ eq '') {
+            is_literal_value($chunk->{$_})
+              ? carp 'Hash-pairs consisting of an empty string with a literal are deprecated, use -and => [ $literal ] instead'
+              : $self->throw_exception("Supplying an empty left hand side argument is not supported in hash-pairs")
+            ;
+          }
+
+          push @pairs, $_ => $chunk->{$_};
+        }
+      }
+      elsif (ref $chunk eq 'ARRAY') {
+        push @pairs, -or => $chunk
+          if @$chunk;
+      }
+      elsif ( ! length ref $chunk) {
+
+        # Match SQLA 1.79 behavior
+        $self->throw_exception("Supplying an empty left hand side argument is not supported in array-pairs")
+          if $where_is_anded_array and (! defined $chunk or $chunk eq '');
+
+        push @pairs, $chunk, shift @pieces;
+      }
+      else {
+        push @pairs, '', $chunk;
+      }
+    }
+
+    return unless @pairs;
+
+    my @conds = $self->_collapse_cond_unroll_pairs(\@pairs)
+      or return;
+
+    # Consolidate various @conds back into something more compact
+    for my $c (@conds) {
+      if (ref $c ne 'HASH') {
+        push @{$fin->{-and}}, $c;
+      }
+      else {
+        for my $col (sort keys %$c) {
+
+          # consolidate all -and nodes
+          if ($col =~ /^\-and$/i) {
+            push @{$fin->{-and}},
+              ref $c->{$col} eq 'ARRAY' ? @{$c->{$col}}
+            : ref $c->{$col} eq 'HASH' ? %{$c->{$col}}
+            : { $col => $c->{$col} }
+            ;
+          }
+          elsif ($col =~ /^\-/) {
+            push @{$fin->{-and}}, { $col => $c->{$col} };
+          }
+          elsif (exists $fin->{$col}) {
+            $fin->{$col} = [ -and => map {
+              (ref $_ eq 'ARRAY' and ($_->[0]||'') =~ /^\-and$/i )
+                ? @{$_}[1..$#$_]
+                : $_
+              ;
+            } ($fin->{$col}, $c->{$col}) ];
+          }
+          else {
+            $fin->{$col} = $c->{$col};
+          }
+        }
+      }
+    }
+  }
+  elsif (ref $where eq 'ARRAY') {
+    # we are always at top-level here, it is safe to dump empty *standalone* pieces
+    my $fin_idx;
+
+    for (my $i = 0; $i <= $#$where; $i++ ) {
+
+      # Match SQLA 1.79 behavior
+      $self->throw_exception(
+        "Supplying an empty left hand side argument is not supported in array-pairs"
+      ) if (! defined $where->[$i] or ! length $where->[$i]);
+
+      my $logic_mod = lc ( ($where->[$i] =~ /^(\-(?:and|or))$/i)[0] || '' );
+
+      if ($logic_mod) {
+        $i++;
+        $self->throw_exception("Unsupported top-level op/arg pair: [ $logic_mod => $where->[$i] ]")
+          unless ref $where->[$i] eq 'HASH' or ref $where->[$i] eq 'ARRAY';
+
+        my $sub_elt = $self->_collapse_cond({ $logic_mod => $where->[$i] })
+          or next;
+
+        my @keys = keys %$sub_elt;
+        if ( @keys == 1 and $keys[0] !~ /^\-/ ) {
+          $fin_idx->{ "COL_$keys[0]_" . serialize $sub_elt } = $sub_elt;
+        }
+        else {
+          $fin_idx->{ "SER_" . serialize $sub_elt } = $sub_elt;
+        }
+      }
+      elsif (! length ref $where->[$i] ) {
+        my $sub_elt = $self->_collapse_cond({ @{$where}[$i, $i+1] })
+          or next;
+
+        $fin_idx->{ "COL_$where->[$i]_" . serialize $sub_elt } = $sub_elt;
+        $i++;
+      }
+      else {
+        $fin_idx->{ "SER_" . serialize $where->[$i] } = $self->_collapse_cond( $where->[$i] ) || next;
+      }
+    }
+
+    if (! $fin_idx) {
+      return;
+    }
+    elsif ( keys %$fin_idx == 1 ) {
+      $fin = (values %$fin_idx)[0];
+    }
+    else {
+      my @or;
+
+      # at this point everything is at most one level deep - unroll if needed
+      for (sort keys %$fin_idx) {
+        if ( ref $fin_idx->{$_} eq 'HASH' and keys %{$fin_idx->{$_}} == 1 ) {
+          my ($l, $r) = %{$fin_idx->{$_}};
+
+          if (
+            ref $r eq 'ARRAY'
+              and
+            (
+              ( @$r == 1 and $l =~ /^\-and$/i )
+                or
+              $l =~ /^\-or$/i
+            )
+          ) {
+            push @or, @$r
+          }
+
+          elsif (
+            ref $r eq 'HASH'
+              and
+            keys %$r == 1
+              and
+            $l =~ /^\-(?:and|or)$/i
+          ) {
+            push @or, %$r;
+          }
+
+          else {
+            push @or, $l, $r;
+          }
+        }
+        else {
+          push @or, $fin_idx->{$_};
+        }
+      }
+
+      $fin->{-or} = \@or;
+    }
+  }
+  else {
+    # not a hash not an array
+    $fin = { -and => [ $where ] };
+  }
+
+  # unroll single-element -and's
+  while (
+    $fin->{-and}
+      and
+    @{$fin->{-and}} < 2
+  ) {
+    my $and = delete $fin->{-and};
+    last if @$and == 0;
 
-  for (0 .. $#ord_cols) {
+    # at this point we have @$and == 1
     if (
-      ! $colinfos->{$ord_cols[$_]}
-        or
-      $colinfos->{$ord_cols[$_]}{-result_source} != $main_rsrc
+      ref $and->[0] eq 'HASH'
+        and
+      ! grep { exists $fin->{$_} } keys %{$and->[0]}
     ) {
-      $#ord_cols =  $_ - 1;
+      $fin = {
+        %$fin, %{$and->[0]}
+      };
+    }
+    else {
+      $fin->{-and} = $and;
       last;
     }
   }
 
-  # we just truncated it above
-  return unless @ord_cols;
+  # compress same-column conds found in $fin
+  for my $col ( grep { $_ !~ /^\-/ } keys %$fin ) {
+    next unless ref $fin->{$col} eq 'ARRAY' and ($fin->{$col}[0]||'') =~ /^\-and$/i;
+    my $val_bag = { map {
+      (! defined $_ )                          ? ( UNDEF => undef )
+    : ( ! length ref $_ or is_plain_value $_ ) ? ( "VAL_$_" => $_ )
+    : ( ( 'SER_' . serialize $_ ) => $_ )
+    } @{$fin->{$col}}[1 .. $#{$fin->{$col}}] };
+
+    if (keys %$val_bag == 1 ) {
+      ($fin->{$col}) = values %$val_bag;
+    }
+    else {
+      $fin->{$col} = [ -and => map { $val_bag->{$_} } sort keys %$val_bag ];
+    }
+  }
 
-  my $order_portion_ci = { map {
-    $colinfos->{$_}{-colname} => $colinfos->{$_},
-    $colinfos->{$_}{-fq_colname} => $colinfos->{$_},
-  } @ord_cols };
+  return keys %$fin ? $fin : ();
+}
 
-  # since all we check here are the start of the order_by belonging to the
-  # top level $rsrc, a present identifying set will mean that the resultset
-  # is ordered by its leftmost table in a stable manner
-  #
-  # RV of _identifying_column_set contains unqualified names only
-  my $unqualified_idset = $main_rsrc->_identifying_column_set({
-    ( $where ? %{
-      $self->_resolve_column_info(
-        $main_rsrc, $self->_extract_fixed_condition_columns($where)
-      )
-    } : () ),
-    %$order_portion_ci
-  }) or return;
-
-  my $ret_info;
-  my %unqualified_idcols_from_order = map {
-    $order_portion_ci->{$_} ? ( $_ => $order_portion_ci->{$_} ) : ()
-  } @$unqualified_idset;
-
-  # extra optimization - cut the order_by at the end of the identifying set
-  # (just in case the user was stupid and overlooked the obvious)
-  for my $i (0 .. $#ord_cols) {
-    my $col = $ord_cols[$i];
-    my $unqualified_colname = $order_portion_ci->{$col}{-colname};
-    $ret_info->{$col} = { %{$order_portion_ci->{$col}}, -idx_in_order_subset => $i };
-    delete $unqualified_idcols_from_order{$ret_info->{$col}{-colname}};
-
-    # we didn't reach the end of the identifying portion yet
-    return $ret_info unless keys %unqualified_idcols_from_order;
-  }
-
-  die 'How did we get here...';
+sub _collapse_cond_unroll_pairs {
+  my ($self, $pairs) = @_;
+
+  my @conds;
+
+  while (@$pairs) {
+    my ($lhs, $rhs) = splice @$pairs, 0, 2;
+
+    if ($lhs eq '') {
+      push @conds, $self->_collapse_cond($rhs);
+    }
+    elsif ( $lhs =~ /^\-and$/i ) {
+      push @conds, $self->_collapse_cond($rhs, (ref $rhs eq 'ARRAY'));
+    }
+    elsif ( $lhs =~ /^\-or$/i ) {
+      push @conds, $self->_collapse_cond(
+        (ref $rhs eq 'HASH') ? [ map { $_ => $rhs->{$_} } sort keys %$rhs ] : $rhs
+      );
+    }
+    else {
+      if (ref $rhs eq 'HASH' and ! keys %$rhs) {
+        # FIXME - SQLA seems to be doing... nothing...?
+      }
+      # normalize top level -ident, for saner extract_fixed_condition_columns code
+      elsif (ref $rhs eq 'HASH' and keys %$rhs == 1 and exists $rhs->{-ident}) {
+        push @conds, { $lhs => { '=', $rhs } };
+      }
+      elsif (ref $rhs eq 'HASH' and keys %$rhs == 1 and exists $rhs->{-value} and is_plain_value $rhs->{-value}) {
+        push @conds, { $lhs => $rhs->{-value} };
+      }
+      elsif (ref $rhs eq 'HASH' and keys %$rhs == 1 and exists $rhs->{'='}) {
+        if ( length ref $rhs->{'='} and is_literal_value $rhs->{'='} ) {
+          push @conds, { $lhs => $rhs };
+        }
+        else {
+          for my $p ($self->_collapse_cond_unroll_pairs([ $lhs => $rhs->{'='} ])) {
+
+            # extra sanity check
+            if (keys %$p > 1) {
+              require Data::Dumper::Concise;
+              local $Data::Dumper::Deepcopy = 1;
+              $self->throw_exception(
+                "Internal error: unexpected collapse unroll:"
+              . Data::Dumper::Concise::Dumper { in => { $lhs => $rhs }, out => $p }
+              );
+            }
+
+            my ($l, $r) = %$p;
+
+            push @conds, (
+              ! length ref $r
+                or
+              # the unroller recursion may return a '=' prepended value already
+              ref $r eq 'HASH' and keys %$rhs == 1 and exists $rhs->{'='}
+                or
+              is_plain_value($r)
+            )
+              ? { $l => $r }
+              : { $l => { '=' => $r } }
+            ;
+          }
+        }
+      }
+      elsif (ref $rhs eq 'ARRAY') {
+        # some of these conditionals encounter multi-values - roll them out using
+        # an unshift, which will cause extra looping in the while{} above
+        if (! @$rhs ) {
+          push @conds, { $lhs => [] };
+        }
+        elsif ( ($rhs->[0]||'') =~ /^\-(?:and|or)$/i ) {
+          $self->throw_exception("Value modifier not followed by any values: $lhs => [ $rhs->[0] ] ")
+            if  @$rhs == 1;
+
+          if( $rhs->[0] =~ /^\-and$/i ) {
+            unshift @$pairs, map { $lhs => $_ } @{$rhs}[1..$#$rhs];
+          }
+          # if not an AND then it's an OR
+          elsif(@$rhs == 2) {
+            unshift @$pairs, $lhs => $rhs->[1];
+          }
+          else {
+            push @conds, { $lhs => [ @{$rhs}[1..$#$rhs] ] };
+          }
+        }
+        elsif (@$rhs == 1) {
+          unshift @$pairs, $lhs => $rhs->[0];
+        }
+        else {
+          push @conds, { $lhs => $rhs };
+        }
+      }
+      # unroll func + { -value => ... }
+      elsif (
+        ref $rhs eq 'HASH'
+          and
+        ( my ($subop) = keys %$rhs ) == 1
+          and
+        length ref ((values %$rhs)[0])
+          and
+        my $vref = is_plain_value( (values %$rhs)[0] )
+      ) {
+        push @conds, { $lhs => { $subop => $$vref } }
+      }
+      else {
+        push @conds, { $lhs => $rhs };
+      }
+    }
+  }
+
+  return @conds;
 }
 
-# returns an arrayref of column names which *definitely* have some
-# sort of non-nullable equality requested in the given condition
-# specification. This is used to figure out if a resultset is
-# constrained to a column which is part of a unique constraint,
-# which in turn allows us to better predict how ordering will behave
-# etc.
+# Analyzes a given condition and attempts to extract all columns
+# with a definitive fixed-condition criteria. Returns a hashref
+# of k/v pairs suitable to be passed to set_columns(), with a
+# MAJOR CAVEAT - multi-value (contradictory) equalities are still
+# represented as a reference to the UNRESOVABLE_CONDITION constant
+# The reason we do this is that some codepaths only care about the
+# codition being stable, as opposed to actually making sense
+#
+# The normal mode is used to figure out if a resultset is constrained
+# to a column which is part of a unique constraint, which in turn
+# allows us to better predict how ordering will behave etc.
+#
+# With the optional "consider_nulls" boolean argument, the function
+# is instead used to infer inambiguous values from conditions
+# (e.g. the inheritance of resultset conditions on new_result)
 #
-# this is a rudimentary, incomplete, and error-prone extractor
-# however this is OK - it is conservative, and if we can not find
-# something that is in fact there - the stack will recover gracefully
-# Also - DQ and the mst it rode in on will save us all RSN!!!
 sub _extract_fixed_condition_columns {
-  my ($self, $where) = @_;
+  my ($self, $where, $consider_nulls) = @_;
+  my $where_hash = $self->_collapse_cond($_[1]);
 
-  return unless ref $where eq 'HASH';
+  my $res = {};
+  my ($c, $v);
+  for $c (keys %$where_hash) {
+    my $vals;
 
-  my @cols;
-  for my $lhs (keys %$where) {
-    if ($lhs =~ /^\-and$/i) {
-      push @cols, ref $where->{$lhs} eq 'ARRAY'
-        ? ( map { @{ $self->_extract_fixed_condition_columns($_) } } @{$where->{$lhs}} )
-        : @{ $self->_extract_fixed_condition_columns($where->{$lhs}) }
-      ;
+    if (!defined ($v = $where_hash->{$c}) ) {
+      $vals->{UNDEF} = $v if $consider_nulls
+    }
+    elsif (
+      ref $v eq 'HASH'
+        and
+      keys %$v == 1
+    ) {
+      if (exists $v->{-value}) {
+        if (defined $v->{-value}) {
+          $vals->{"VAL_$v->{-value}"} = $v->{-value}
+        }
+        elsif( $consider_nulls ) {
+          $vals->{UNDEF} = $v->{-value};
+        }
+      }
+      # do not need to check for plain values - _collapse_cond did it for us
+      elsif(
+        length ref $v->{'='}
+          and
+        (
+          ( ref $v->{'='} eq 'HASH' and keys %{$v->{'='}} == 1 and exists $v->{'='}{-ident} )
+            or
+          is_literal_value($v->{'='})
+        )
+       ) {
+        $vals->{ 'SER_' . serialize $v->{'='} } = $v->{'='};
+      }
+    }
+    elsif (
+      ! length ref $v
+        or
+      is_plain_value ($v)
+    ) {
+      $vals->{"VAL_$v"} = $v;
+    }
+    elsif (ref $v eq 'ARRAY' and ($v->[0]||'') eq '-and') {
+      for ( @{$v}[1..$#$v] ) {
+        my $subval = $self->_extract_fixed_condition_columns({ $c => $_ }, 'consider nulls');  # always fish nulls out on recursion
+        next unless exists $subval->{$c};  # didn't find anything
+        $vals->{
+          ! defined $subval->{$c}                                        ? 'UNDEF'
+        : ( ! length ref $subval->{$c} or is_plain_value $subval->{$c} ) ? "VAL_$subval->{$c}"
+        : ( 'SER_' . serialize $subval->{$c} )
+        } = $subval->{$c};
+      }
     }
-    elsif ($lhs !~ /^\-/) {
-      my $val = $where->{$lhs};
 
-      push @cols, $lhs if (defined $val and (
-        ! ref $val
-          or
-        (ref $val eq 'HASH' and keys %$val == 1 and defined $val->{'='})
-      ));
+    if (keys %$vals == 1) {
+      ($res->{$c}) = (values %$vals)
+        unless !$consider_nulls and exists $vals->{UNDEF};
+    }
+    elsif (keys %$vals > 1) {
+      $res->{$c} = UNRESOLVABLE_CONDITION;
     }
   }
-  return \@cols;
+
+  $res;
 }
 
 1;