[Bast-commits] r9461 - in DBIx-Class/0.08/trunk: . lib/DBIx/Class lib/DBIx/Class/Storage t/lib/DBICTest/Schema t/sqlahacks/limit_dialects

ribasushi at dev.catalyst.perl.org ribasushi at dev.catalyst.perl.org
Sun May 30 22:17:29 GMT 2010


Author: ribasushi
Date: 2010-05-30 23:17:29 +0100 (Sun, 30 May 2010)
New Revision: 9461

Added:
   DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/generic_subq.t
Modified:
   DBIx-Class/0.08/trunk/Changes
   DBIx-Class/0.08/trunk/lib/DBIx/Class/SQLAHacks.pm
   DBIx-Class/0.08/trunk/lib/DBIx/Class/Storage/DBI.pm
   DBIx-Class/0.08/trunk/t/lib/DBICTest/Schema/BooksInLibrary.pm
   DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/toplimit.t
Log:
Rewrite GenericSubQ from SQLA::L to be actually useful
Since it now works it is no longer necessary to turn on softlimit when genericsubq is detected
Switch all sprintf()ed limit/offset specs to unsigned integers
Lower the default rows-without-offset to 2^32

Modified: DBIx-Class/0.08/trunk/Changes
===================================================================
--- DBIx-Class/0.08/trunk/Changes	2010-05-30 09:40:12 UTC (rev 9460)
+++ DBIx-Class/0.08/trunk/Changes	2010-05-30 22:17:29 UTC (rev 9461)
@@ -22,6 +22,9 @@
           resultsets
         - MSSQL limits now don't require nearly as many applications of
           the unsafe_subselect_ok attribute, due to optimized queries
+        - Support for Generic Subquery limit "emulation" - awfully slow
+          and inefficient but works on almost any db, and is preferred
+          to a soft-limit
         - Fix as_subselect_rs to not inject resultset class-wide where
           conditions outside of the resulting subquery
         - Fix nasty potentially data-eating bug when deleting/updating

Modified: DBIx-Class/0.08/trunk/lib/DBIx/Class/SQLAHacks.pm
===================================================================
--- DBIx-Class/0.08/trunk/lib/DBIx/Class/SQLAHacks.pm	2010-05-30 09:40:12 UTC (rev 9460)
+++ DBIx-Class/0.08/trunk/lib/DBIx/Class/SQLAHacks.pm	2010-05-30 22:17:29 UTC (rev 9461)
@@ -48,29 +48,25 @@
 
 # !!! THIS IS ALSO HORRIFIC !!! /me ashamed
 #
-# generate inner/outer select lists for various limit dialects
+# Generates inner/outer select lists for various limit dialects
 # which result in one or more subqueries (e.g. RNO, Top, RowNum)
 # Any non-root-table columns need to have their table qualifier
 # turned into a column alias (otherwise names in subqueries clash
 # and/or lose their source table)
 #
-# returns inner/outer strings of SQL QUOTED selectors with aliases
+# Returns inner/outer strings of SQL QUOTED selectors with aliases
 # (to be used in whatever select statement), and an alias index hashref
 # of QUOTED SEL => QUOTED ALIAS pairs (to maybe be used for string-subst
-# higher up)
-#
-# If the $scan_order option is supplied, it signals that the limit dialect
-# needs to order the outer side of the query, which in turn means that the
-# inner select needs to bring out columns used in implicit (non-selected)
-# orders, and the order condition itself needs to be realiased to the proper
-# names in the outer query.
-#
-# In this case ($scan_order os true) we also return a hashref (order doesn't
-# matter) of QUOTED EXTRA-SEL => QUOTED ALIAS pairs, which is a list of extra
-# selectors that do *not* exist in the original select list
+# higher up).
+# If an order_by is supplied, the inner select needs to bring out columns
+# used in implicit (non-selected) orders, and the order condition itself
+# needs to be realiased to the proper names in the outer query. Thus we
+# also return a hashref (order doesn't matter) of QUOTED EXTRA-SEL =>
+# QUOTED ALIAS pairs, which is a list of extra selectors that do *not*
+# exist in the original select list
 
 sub _subqueried_limit_attrs {
-  my ($self, $rs_attrs, $scan_order) = @_;
+  my ($self, $rs_attrs) = @_;
 
   croak 'Limit dialect implementation usable only in the context of DBIC (missing $rs_attrs)'
     unless ref ($rs_attrs) eq 'HASH';
@@ -104,10 +100,12 @@
     $in_sel_index->{$sql_sel}++;
     $in_sel_index->{$self->_quote ($sql_alias)}++ if $sql_alias;
 
-# this *may* turn out to be necessary, not sure yet
-#    my ($sql_unqualified_sel) = $sql_sel =~ / $re_sep (.+) $/x
-#      if ! ref $s;
-#    $in_sel_index->{$sql_unqualified_sel}++;
+    # record unqualified versions too, so we do not have
+    # to reselect the same column twice (in qualified and
+    # unqualified form)
+    if (! ref $s && $sql_sel =~ / $re_sep (.+) $/x) {
+      $in_sel_index->{$1}++;
+    }
   }
 
 
@@ -130,20 +128,20 @@
     }
   }
 
+  # see if the order gives us anything
   my %extra_order_sel;
-  if ($scan_order) {
-    for my $chunk ($self->_order_by_chunks ($rs_attrs->{order_by})) {
-      # order with bind
-      $chunk = $chunk->[0] if (ref $chunk) eq 'ARRAY';
-      $chunk =~ s/\s+ (?: ASC|DESC ) \s* $//ix;
+  for my $chunk ($self->_order_by_chunks ($rs_attrs->{order_by})) {
+    # order with bind
+    $chunk = $chunk->[0] if (ref $chunk) eq 'ARRAY';
+    $chunk =~ s/\s+ (?: ASC|DESC ) \s* $//ix;
 
-      next if $in_sel_index->{$chunk};
+    next if $in_sel_index->{$chunk};
 
-      $extra_order_sel{$chunk} ||= $self->_quote (
-        'ORDER__BY__' . scalar keys %extra_order_sel
-      );
-    }
+    $extra_order_sel{$chunk} ||= $self->_quote (
+      'ORDER__BY__' . scalar keys %extra_order_sel
+    );
   }
+
   return (
     (map { join (', ', @$_ ) } (
       \@in_sel,
@@ -163,9 +161,8 @@
     or croak "Unrecognizable SELECT: $sql";
 
   # get selectors, and scan the order_by (if any)
-  my ($in_sel, $out_sel, $alias_map, $extra_order_sel) = $self->_subqueried_limit_attrs (
-    $rs_attrs, 'scan_order_by',
-  );
+  my ($in_sel, $out_sel, $alias_map, $extra_order_sel)
+    = $self->_subqueried_limit_attrs ( $rs_attrs );
 
   # make up an order if none exists
   my $requested_order = (delete $rs_attrs->{order_by}) || $self->_rno_default_order;
@@ -207,7 +204,7 @@
   SELECT $mid_sel, ROW_NUMBER() OVER( $rno_ord ) AS $idx_name FROM (
     SELECT $in_sel ${sql}${group_having}
   ) $qalias
-) $qalias WHERE $idx_name BETWEEN %d AND %d
+) $qalias WHERE $idx_name BETWEEN %u AND %u
 
 EOS
 
@@ -229,10 +226,10 @@
 
   return sprintf ('SELECT %s%s%s%s',
     $offset
-      ? sprintf ('SKIP %d ', $offset)
+      ? sprintf ('SKIP %u ', $offset)
       : ''
     ,
-    sprintf ('FIRST %d ', $rows),
+    sprintf ('FIRST %u ', $rows),
     $sql,
     $self->_parse_rs_attrs ($rs_attrs),
   );
@@ -246,9 +243,9 @@
     or croak "Unrecognizable SELECT: $sql";
 
   return sprintf ('SELECT %s%s%s%s',
-    sprintf ('FIRST %d ', $rows),
+    sprintf ('FIRST %u ', $rows),
     $offset
-      ? sprintf ('SKIP %d ', $offset)
+      ? sprintf ('SKIP %u ', $offset)
       : ''
     ,
     $sql,
@@ -276,7 +273,7 @@
   SELECT $outsel, ROWNUM $idx_name FROM (
     SELECT $insel ${sql}${order_group_having}
   ) $qalias
-) $qalias WHERE $idx_name BETWEEN %d AND %d
+) $qalias WHERE $idx_name BETWEEN %u AND %u
 
 EOS
 
@@ -294,7 +291,7 @@
 
   # get selectors
   my ($in_sel, $out_sel, $alias_map, $extra_order_sel)
-    = $self->_subqueried_limit_attrs ($rs_attrs, 'outer_order_by');
+    = $self->_subqueried_limit_attrs ($rs_attrs);
 
   my $requested_order = delete $rs_attrs->{order_by};
 
@@ -359,7 +356,7 @@
 
   my $quoted_rs_alias = $self->_quote ($rs_attrs->{alias});
 
-  $sql = sprintf ('SELECT TOP %d %s %s %s %s',
+  $sql = sprintf ('SELECT TOP %u %s %s %s %s',
     $rows + ($offset||0),
     $in_sel,
     $sql,
@@ -367,7 +364,7 @@
     $order_by_inner,
   );
 
-  $sql = sprintf ('SELECT TOP %d %s FROM ( %s ) %s %s',
+  $sql = sprintf ('SELECT TOP %u %s FROM ( %s ) %s %s',
     $rows,
     $mid_sel,
     $sql,
@@ -375,7 +372,7 @@
     $order_by_reversed,
   ) if $offset;
 
-  $sql = sprintf ('SELECT TOP %d %s FROM ( %s ) %s %s',
+  $sql = sprintf ('SELECT TOP %u %s FROM ( %s ) %s %s',
     $rows,
     $out_sel,
     $sql,
@@ -383,10 +380,116 @@
     $order_by_requested,
   ) if ( ($offset && $order_by_requested) || ($mid_sel ne $out_sel) );
 
+  $sql =~ s/\s*\n\s*/ /g;   # easier to read in the debugger
   return $sql;
 }
 
+# This is the most evil limit "dialect" (more of a hack) for *really*
+# stupid databases. It works by ordering the set by some unique column,
+# and calculating amount of rows that have a less-er value (thus
+# emulating a RowNum-like index). Of course this implies the set can
+# only be ordered by a single unique columns.
+sub _GenericSubQ {
+  my ($self, $sql, $rs_attrs, $rows, $offset) = @_;
 
+  my $root_rsrc = $rs_attrs->{_rsroot_source_handle}->resolve;
+  my $root_tbl_name = $root_rsrc->name;
+
+  # mangle the input sql as we will be replacing the selector
+  $sql =~ s/^ \s* SELECT \s+ .+? \s+ (?= \b FROM \b )//ix
+    or croak "Unrecognizable SELECT: $sql";
+
+  my ($order_by, @rest) = do {
+    local $self->{quote_char};
+    $self->_order_by_chunks ($rs_attrs->{order_by})
+  };
+
+  unless (
+    $order_by
+      &&
+    ! @rest
+      &&
+    ( ! ref $order_by
+        ||
+      ( ref $order_by eq 'ARRAY' and @$order_by == 1 )
+    )
+  ) {
+    croak (
+      'Generic Subquery Limit does not work on resultsets without an order, or resultsets '
+    . 'with complex order criteria (multicolumn and/or functions). Provide a single, '
+    . 'unique-column order criteria.'
+    );
+  }
+
+  ($order_by) = @$order_by if ref $order_by;
+
+  $order_by =~ s/\s+ ( ASC|DESC ) \s* $//ix;
+  my $direction = lc ($1 || 'asc');
+
+  my ($unq_sort_col) = $order_by =~ /(?:^|\.)([^\.]+)$/;
+
+  my $inf = $root_rsrc->storage->_resolve_column_info (
+    $rs_attrs->{from}, [$order_by, $unq_sort_col]
+  );
+
+  my $ord_colinfo = $inf->{$order_by} || croak "Unable to determine source of order-criteria '$order_by'";
+
+  if ($ord_colinfo->{-result_source}->name ne $root_tbl_name) {
+    croak "Generic Subquery Limit order criteria can be only based on the root-source '"
+        . $root_rsrc->source_name . "' (aliased as '$rs_attrs->{alias}')";
+  }
+
+  # make sure order column is qualified
+  $order_by = "$rs_attrs->{alias}.$order_by"
+    unless $order_by =~ /^$rs_attrs->{alias}\./;
+
+  my $is_u;
+  my $ucs = { $root_rsrc->unique_constraints };
+  for (values %$ucs ) {
+    if (@$_ == 1 && "$rs_attrs->{alias}.$_->[0]" eq $order_by) {
+      $is_u++;
+      last;
+    }
+  }
+  croak "Generic Subquery Limit order criteria column '$order_by' must be unique (no unique constraint found)"
+    unless $is_u;
+
+  my ($in_sel, $out_sel, $alias_map, $extra_order_sel)
+    = $self->_subqueried_limit_attrs ($rs_attrs);
+
+  my $cmp_op = $direction eq 'desc' ? '>' : '<';
+  my $count_tbl_alias = 'rownum__emulation';
+
+  my $order_group_having = $self->_parse_rs_attrs($rs_attrs);
+
+  # add the order supplement (if any) as this is what will be used for the outer WHERE
+  $in_sel .= ", $_" for keys %{$extra_order_sel||{}};
+
+  $sql = sprintf (<<EOS,
+SELECT $out_sel
+  FROM (
+    SELECT $in_sel ${sql}${order_group_having}
+  ) %s
+WHERE ( SELECT COUNT(*) FROM %s %s WHERE %s $cmp_op %s ) %s
+EOS
+    ( map { $self->_quote ($_) } (
+      $rs_attrs->{alias},
+      $root_tbl_name,
+      $count_tbl_alias,
+      "$count_tbl_alias.$unq_sort_col",
+      $order_by,
+    )),
+    $offset
+      ? sprintf ('BETWEEN %u AND %u', $offset, $offset + $rows - 1)
+      : sprintf ('< %u', $rows )
+    ,
+  );
+
+  $sql =~ s/\s*\n\s*/ /g;   # easier to read in the debugger
+  return $sql;
+}
+
+
 # While we're at it, this should make LIMIT queries more efficient,
 #  without digging into things too deeply
 sub _find_syntax {

Modified: DBIx-Class/0.08/trunk/lib/DBIx/Class/Storage/DBI.pm
===================================================================
--- DBIx-Class/0.08/trunk/lib/DBIx/Class/Storage/DBI.pm	2010-05-30 09:40:12 UTC (rev 9460)
+++ DBIx-Class/0.08/trunk/lib/DBIx/Class/Storage/DBI.pm	2010-05-30 22:17:29 UTC (rev 9461)
@@ -1922,19 +1922,13 @@
   }
 
   # adjust limits
-  if (
-    $attrs->{software_limit}
-      ||
-    $sql_maker->_default_limit_syntax eq "GenericSubQ"
-  ) {
-    $attrs->{software_limit} = 1;
-  }
-  else {
+  if (defined $attrs->{rows}) {
     $self->throw_exception("rows attribute must be positive if present")
-      if (defined($attrs->{rows}) && !($attrs->{rows} > 0));
-
+      unless $attrs->{rows} > 0;
+  }
+  elsif (defined $attrs->{offset}) {
     # MySQL actually recommends this approach.  I cringe.
-    $attrs->{rows} = 2**48 if not defined $attrs->{rows} and defined $attrs->{offset};
+    $attrs->{rows} = 2**32;
   }
 
   my @limit;

Modified: DBIx-Class/0.08/trunk/t/lib/DBICTest/Schema/BooksInLibrary.pm
===================================================================
--- DBIx-Class/0.08/trunk/t/lib/DBICTest/Schema/BooksInLibrary.pm	2010-05-30 09:40:12 UTC (rev 9460)
+++ DBIx-Class/0.08/trunk/t/lib/DBICTest/Schema/BooksInLibrary.pm	2010-05-30 22:17:29 UTC (rev 9461)
@@ -27,6 +27,8 @@
 );
 __PACKAGE__->set_primary_key('id');
 
+__PACKAGE__->add_unique_constraint (['title']);
+
 __PACKAGE__->resultset_attributes({where => { source => "Library" } });
 
 __PACKAGE__->belongs_to ( owner => 'DBICTest::Schema::Owners', 'owner' );

Added: DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/generic_subq.t
===================================================================
--- DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/generic_subq.t	                        (rev 0)
+++ DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/generic_subq.t	2010-05-30 22:17:29 UTC (rev 9461)
@@ -0,0 +1,125 @@
+use strict;
+use warnings;
+
+use Test::More;
+use lib qw(t/lib);
+use DBICTest;
+use DBIC::SqlMakerTest;
+
+my $schema = DBICTest->init_schema;
+
+$schema->storage->_sql_maker->limit_dialect ('GenericSubQ');
+
+my $rs = $schema->resultset ('BooksInLibrary')->search ({}, {
+  '+columns' => [{ owner_name => 'owner.name' }],
+  join => 'owner',
+  rows => 2,
+  order_by => 'me.title',
+});
+
+is_same_sql_bind(
+  $rs->as_query,
+  '(
+    SELECT  id, source, owner, title, price,
+            owner_name
+      FROM (
+        SELECT  me.id, me.source, me.owner, me.title, me.price,
+                owner.name AS owner_name
+          FROM books me
+          JOIN owners owner ON owner.id = me.owner
+        WHERE ( source = ? )
+        ORDER BY me.title
+      ) me
+    WHERE
+      (
+        SELECT COUNT(*)
+          FROM books rownum__emulation
+        WHERE rownum__emulation.title < me.title
+      ) < 2
+  )',
+  [  [ 'source', 'Library' ] ],
+);
+
+is_deeply (
+  [ $rs->get_column ('title')->all ],
+  ['Best Recipe Cookbook', 'Dynamical Systems'],
+  'Correct columns selected with rows',
+);
+
+$schema->storage->_sql_maker->quote_char ('"');
+$schema->storage->_sql_maker->name_sep ('.');
+
+$rs = $schema->resultset ('BooksInLibrary')->search ({}, {
+  order_by => { -desc => 'title' },
+  '+select' => ['owner.name'],
+  '+as' => ['owner.name'],
+  join => 'owner',
+  rows => 3,
+  offset => 1,
+});
+
+is_same_sql_bind(
+  $rs->as_query,
+  '(
+    SELECT  "id", "source", "owner", "title", "price",
+            "owner__name"
+      FROM (
+        SELECT  "me"."id", "me"."source", "me"."owner", "me"."title", "me"."price",
+                "owner"."name" AS "owner__name"
+          FROM "books" "me"
+          JOIN "owners" "owner" ON "owner"."id" = "me"."owner"
+        WHERE ( "source" = ? )
+        ORDER BY "title" DESC
+      ) "me"
+    WHERE
+      (
+        SELECT COUNT(*)
+          FROM "books" "rownum__emulation"
+        WHERE "rownum__emulation"."title" > "me"."title"
+      ) BETWEEN 1 AND 3
+  )',
+  [ [ 'source', 'Library' ] ],
+);
+
+is_deeply (
+  [ $rs->get_column ('title')->all ],
+  [ 'Dynamical Systems', 'Best Recipe Cookbook' ],
+  'Correct columns selected with rows',
+);
+
+$rs = $schema->resultset ('BooksInLibrary')->search ({}, {
+  order_by => 'title',
+  'select' => ['owner.name'],
+  'as' => ['owner_name'],
+  join => 'owner',
+  offset => 1,
+});
+
+is_same_sql_bind(
+  $rs->as_query,
+  '(
+    SELECT "owner_name"
+      FROM (
+        SELECT "owner"."name" AS "owner_name", "title"
+          FROM "books" "me"
+          JOIN "owners" "owner" ON "owner"."id" = "me"."owner"
+        WHERE ( "source" = ? )
+        ORDER BY "title"
+      ) "me"
+    WHERE
+      (
+        SELECT COUNT(*)
+          FROM "books" "rownum__emulation"
+        WHERE "rownum__emulation"."title" < "me"."title"
+      ) BETWEEN 1 AND 4294967295
+  )',
+  [ [ 'source', 'Library' ] ],
+);
+
+is_deeply (
+  [ $rs->get_column ('owner_name')->all ],
+  [ ('Newton') x 2 ],
+  'Correct columns selected with rows',
+);
+
+done_testing;

Modified: DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/toplimit.t
===================================================================
--- DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/toplimit.t	2010-05-30 09:40:12 UTC (rev 9460)
+++ DBIx-Class/0.08/trunk/t/sqlahacks/limit_dialects/toplimit.t	2010-05-30 22:17:29 UTC (rev 9461)
@@ -153,19 +153,19 @@
         SELECT TOP 2 id, source, owner, title, price
           FROM (
             SELECT TOP 2
-                id, source, owner, title, price, ORDER__BY__1
+                id, source, owner, title, price
               FROM (
                 SELECT TOP 5
-                    me.id, me.source, me.owner, me.title, me.price, title AS ORDER__BY__1
+                    me.id, me.source, me.owner, me.title, me.price
                   FROM books me
                   JOIN owners owner ON owner.id = me.owner
                 WHERE ( source = ? )
                 GROUP BY title
                 ORDER BY title
               ) me
-            ORDER BY ORDER__BY__1 DESC
+            ORDER BY title DESC
           ) me
-        ORDER BY ORDER__BY__1
+        ORDER BY title
       ) me
       JOIN owners owner ON owner.id = me.owner
     WHERE ( source = ? )




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