$extra_col,
$extra_order_sel->{$extra_col},
);
-
- $mid_sel .= ', ' . $extra_order_sel->{$extra_col};
}
}
my $idx_name = $self->_quote ('rownum__index');
my $order_group_having = $self->_parse_rs_attrs($rs_attrs);
+
+ # if no offset (e.g. first page) - we can skip one of the subqueries
+ if (! $offset) {
+ push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ];
+
+ return <<EOS;
+SELECT $outsel FROM (
+ SELECT $insel ${stripped_sql}${order_group_having}
+) $qalias WHERE ROWNUM <= ?
+EOS
+ }
+
#
# There are two ways to limit in Oracle, one vastly faster than the other
# on large resultsets: https://decipherinfosys.wordpress.com/2007/08/09/paging-and-countstopkey-optimization/
# ordered by a unique set of columns, it is not safe to use the faster
# method, and the slower BETWEEN query is used instead
#
- # FIXME - this is quite expensive, and doe snot perform caching of any sort
+ # FIXME - this is quite expensive, and does not perform caching of any sort
# as soon as some of the DQ work becomes viable consider switching this
# over
- if ( __order_by_is_unique($rs_attrs) ) {
-
- # if offset is 0 (first page) the we can skip a subquery
- if (! $offset) {
- push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ];
-
- return <<EOS;
-SELECT $outsel FROM (
- SELECT $insel ${stripped_sql}${order_group_having}
-) $qalias WHERE ROWNUM <= ?
-EOS
- }
- else {
- push @{$self->{limit_bind}}, [ $self->__total_bindtype => $offset + $rows ], [ $self->__offset_bindtype => $offset + 1 ];
+ if (
+ $rs_attrs->{order_by}
+ and
+ $rs_attrs->{_rsroot_rsrc}->storage->_order_by_is_stable(
+ $rs_attrs->{from}, $rs_attrs->{order_by}
+ )
+ ) {
+ push @{$self->{limit_bind}}, [ $self->__total_bindtype => $offset + $rows ], [ $self->__offset_bindtype => $offset + 1 ];
- return <<EOS;
+ return <<EOS;
SELECT $outsel FROM (
SELECT $outsel, ROWNUM $idx_name FROM (
SELECT $insel ${stripped_sql}${order_group_having}
) $qalias WHERE ROWNUM <= ?
) $qalias WHERE $idx_name >= ?
EOS
- }
}
else {
push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1 ], [ $self->__total_bindtype => $offset + $rows ];
}
}
-# determine if the supplied order_by contains a unique column (set)
-sub __order_by_is_unique {
- my $rs_attrs = shift;
- my $rsrc = $rs_attrs->{_rsroot_rsrc};
- my $order_by = $rs_attrs->{order_by}
- || return 0;
-
- my $storage = $rsrc->schema->storage;
-
- my @order_by_cols = map { $_->[0] } $storage->_extract_order_criteria($order_by)
- or return 0;
-
- my $colinfo =
- $storage->_resolve_column_info($rs_attrs->{from}, \@order_by_cols);
-
- my $sources = {
- map {( "$_" => $_ )} map { $_->{-result_source} } values %$colinfo
- };
-
- my $supplied_order = {
- map { $_ => 1 }
- grep { exists $colinfo->{$_} and ! $colinfo->{$_}{is_nullable} }
- @order_by_cols
- };
-
- return 0 unless keys %$supplied_order;
-
- for my $uks (
- map { values %$_ } map { +{ $_->unique_constraints } } values %$sources
- ) {
- return 1
- unless first { ! exists $supplied_order->{$_} } @$uks;
- }
-
- return 0;
-}
-
# used by _Top and _FetchFirst below
sub _prep_for_skimming_limit {
my ( $self, $sql, $rs_attrs ) = @_;
my $requested_order = delete $rs_attrs->{order_by};
$r{order_by_requested} = $self->_order_by ($requested_order);
- # make up an order unless supplied
- my $inner_order = ($r{order_by_requested}
- ? $requested_order
- : [ map
+ # make up an order unless supplied or sanity check what we are given
+ my $inner_order;
+ if ($r{order_by_requested}) {
+ $self->throw_exception (
+ 'Unable to safely perform "skimming type" limit with supplied unstable order criteria'
+ ) unless $rs_attrs->{_rsroot_rsrc}->schema->storage->_order_by_is_stable(
+ $rs_attrs->{from},
+ $requested_order
+ );
+
+ $inner_order = $requested_order;
+ }
+ else {
+ $inner_order = [ map
{ "$rs_attrs->{alias}.$_" }
- ( $rs_attrs->{_rsroot_rsrc}->_pri_cols )
- ]
- );
+ ( @{
+ $rs_attrs->{_rsroot_rsrc}->_identifying_column_set
+ ||
+ $self->throw_exception(sprintf(
+ 'Unable to auto-construct stable order criteria for "skimming type" limit '
+ . "dialect based on source '%s'", $rs_attrs->{_rsroot_rsrc}->name) );
+ } )
+ ];
+ }
# localise as we already have all the bind values we need
{
push @{$self->{pre_select_bind}}, @{$self->{order_bind}};
}
+ # if this is a part of something bigger, we need to add back all
+ # the extra order_by's, as they may be relied upon by the outside
+ # of a prefetch or something
+ if ($rs_attrs->{_is_internal_subuery} and keys %$extra_order_sel) {
+ $r{out_sel} .= sprintf ", $extra_order_sel->{$_} AS $_"
+ for sort
+ { $extra_order_sel->{$a} cmp $extra_order_sel->{$b} }
+ grep { $_ !~ /[^\w\-]/ } # ignore functions
+ keys %$extra_order_sel
+ ;
+ }
+
# and this is order re-alias magic
for my $map ($extra_order_sel, $alias_map) {
for my $col (keys %$map) {
my $root_rsrc = $rs_attrs->{_rsroot_rsrc};
my $root_tbl_name = $root_rsrc->name;
- my ($order_by, @rest) = do {
+ my ($first_order_by) = 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 )
- )
- ) {
- $self->throw_exception (
- 'Generic Subquery Limit does not work on resultsets without an order, or resultsets '
- . 'with complex order criteria (multicolumn and/or functions). Provide a single, '
- . 'unique-column order criteria.'
- );
- }
-
- ($order_by) = @$order_by if ref $order_by;
+ map { ref $_ ? $_->[0] : $_ } $self->_order_by_chunks ($rs_attrs->{order_by})
+ } or $self->throw_exception (
+ 'Generic Subquery Limit does not work on resultsets without an order. Provide a single, '
+ . 'unique-column order criteria.'
+ );
- $order_by =~ s/\s+ ( ASC|DESC ) \s* $//ix;
+ $first_order_by =~ s/\s+ ( ASC|DESC ) \s* $//ix;
my $direction = lc ($1 || 'asc');
- my ($unq_sort_col) = $order_by =~ /(?:^|\.)([^\.]+)$/;
+ my ($first_ord_alias, $first_ord_col) = $first_order_by =~ /^ (?: ([^\.]+) \. )? ([^\.]+) $/x;
- my $inf = $root_rsrc->storage->_resolve_column_info (
- $rs_attrs->{from}, [$order_by, $unq_sort_col]
- );
-
- my $ord_colinfo = $inf->{$order_by} || $self->throw_exception("Unable to determine source of order-criteria '$order_by'");
+ $self->throw_exception(sprintf
+ "Generic Subquery Limit order criteria can be only based on the root-source '%s'"
+ . " (aliased as '%s')", $root_rsrc->source_name, $rs_attrs->{alias},
+ ) if ($first_ord_alias and $first_ord_alias ne $rs_attrs->{alias});
- if ($ord_colinfo->{-result_source}->name ne $root_tbl_name) {
- $self->throw_exception(sprintf
- "Generic Subquery Limit order criteria can be only based on the root-source '%s'"
- . " (aliased as '%s')", $root_rsrc->source_name, $rs_attrs->{alias},
- );
- }
+ $first_ord_alias ||= $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;
- }
- }
$self->throw_exception(
- "Generic Subquery Limit order criteria column '$order_by' must be unique (no unique constraint found)"
- ) unless $is_u;
+ "Generic Subquery Limit first order criteria '$first_ord_col' must be unique"
+ ) unless $root_rsrc->_identifying_column_set([$first_ord_col]);
my ($stripped_sql, $in_sel, $out_sel, $alias_map, $extra_order_sel)
= $self->_subqueried_limit_attrs ($sql, $rs_attrs);
$rs_attrs->{alias},
$root_tbl_name,
$count_tbl_alias,
- "$count_tbl_alias.$unq_sort_col",
- $order_by,
+ "$count_tbl_alias.$first_ord_col",
+ "$first_ord_alias.$first_ord_col",
));
}
#
# Returns mangled proto-sql, 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
+# index hashref of QUOTED SEL => QUOTED ALIAS pairs (to maybe be used
# for string-subst 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
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