sub _RowNumberOver {
my ($self, $sql, $rs_attrs, $rows, $offset ) = @_;
- # mangle the input sql as we will be replacing the selector
- $sql =~ s/^ \s* SELECT \s+ .+? \s+ (?= \b FROM \b )//ix
- or $self->throw_exception("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 ( $rs_attrs );
+ my ($stripped_sql, $in_sel, $out_sel, $alias_map, $extra_order_sel)
+ = $self->_subqueried_limit_attrs ( $sql, $rs_attrs );
# make up an order if none exists
my $requested_order = (delete $rs_attrs->{order_by}) || $self->_rno_default_order;
$extra_col,
$extra_order_sel->{$extra_col},
);
-
- $mid_sel .= ', ' . $extra_order_sel->{$extra_col};
}
}
my $qalias = $self->_quote ($rs_attrs->{alias});
my $idx_name = $self->_quote ('rno__row__index');
- $sql = <<EOS;
+ push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1], [ $self->__total_bindtype => $offset + $rows ];
+
+ return <<EOS;
SELECT $out_sel FROM (
SELECT $mid_sel, ROW_NUMBER() OVER( $rno_ord ) AS $idx_name FROM (
- SELECT $in_sel ${sql}${group_having}
+ SELECT $in_sel ${stripped_sql}${group_having}
) $qalias
) $qalias WHERE $idx_name >= ? AND $idx_name <= ?
EOS
- push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1], [ $self->__total_bindtype => $offset + $rows ];
- return $sql;
}
# some databases are happy with OVER (), some need OVER (ORDER BY (SELECT (1)) )
return sprintf ('SELECT %s%s%s%s',
$offset
? do {
- push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset];
+ push @{$self->{pre_select_bind}}, [ $self->__offset_bindtype => $offset];
'SKIP ? '
}
: ''
,
do {
- push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ];
+ push @{$self->{pre_select_bind}}, [ $self->__rows_bindtype => $rows ];
'FIRST ? '
},
$sql,
return sprintf ('SELECT %s%s%s%s',
do {
- push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ];
+ push @{$self->{pre_select_bind}}, [ $self->__rows_bindtype => $rows ];
'FIRST ? '
},
$offset
? do {
- push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset];
+ push @{$self->{pre_select_bind}}, [ $self->__offset_bindtype => $offset];
'SKIP ? '
}
: ''
);
}
+
=head2 RowNum
+Depending on the resultset attributes one of:
+
SELECT * FROM (
SELECT *, ROWNUM rownum__index FROM (
SELECT ...
) WHERE ROWNUM <= ($limit+$offset)
) WHERE rownum__index >= ($offset+1)
+or
+
+ SELECT * FROM (
+ SELECT *, ROWNUM rownum__index FROM (
+ SELECT ...
+ )
+ ) WHERE rownum__index BETWEEN ($offset+1) AND ($limit+$offset)
+
+or
+
+ SELECT * FROM (
+ SELECT ...
+ ) WHERE ROWNUM <= ($limit+1)
+
Supported by B<Oracle>.
=cut
sub _RowNum {
my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_;
- # mangle the input sql as we will be replacing the selector
- $sql =~ s/^ \s* SELECT \s+ .+? \s+ (?= \b FROM \b )//ix
- or $self->throw_exception("Unrecognizable SELECT: $sql");
-
- my ($insel, $outsel) = $self->_subqueried_limit_attrs ($rs_attrs);
+ my ($stripped_sql, $insel, $outsel) = $self->_subqueried_limit_attrs ($sql, $rs_attrs);
my $qalias = $self->_quote ($rs_attrs->{alias});
my $idx_name = $self->_quote ('rownum__index');
my $order_group_having = $self->_parse_rs_attrs($rs_attrs);
- if ($offset) {
+ #
+ # 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/
+ # However Oracle is retarded and does not preserve stable ROWNUM() values
+ # when called twice in the same scope. Therefore unless the resultset is
+ # 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 does not perform caching of any sort
+ # as soon as some of the DQ work becomes viable consider switching this
+ # over
+ if (
+ $rs_attrs->{order_by}
+ and
+ $rs_attrs->{_rsroot_rsrc}->storage->_order_by_is_stable(
+ $rs_attrs->{from}, $rs_attrs->{order_by}
+ )
+ ) {
+ # if offset is 0 (first page) the we can skip a subquery
+ if (! $offset) {
+ push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ];
- push @{$self->{limit_bind}}, [ $self->__total_bindtype => $offset + $rows ], [ $self->__offset_bindtype => $offset + 1 ];
- $sql =<<"EOS";
+ 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 ];
+
+ return <<EOS;
SELECT $outsel FROM (
SELECT $outsel, ROWNUM $idx_name FROM (
- SELECT $insel ${sql}${order_group_having}
+ SELECT $insel ${stripped_sql}${order_group_having}
) $qalias WHERE ROWNUM <= ?
) $qalias WHERE $idx_name >= ?
EOS
+ }
}
else {
- push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ];
- $sql =<<"EOS";
- SELECT $outsel FROM (
- SELECT $insel ${sql}${order_group_having}
- ) $qalias WHERE ROWNUM <= ?
+ push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1 ], [ $self->__total_bindtype => $offset + $rows ];
+
+ return <<EOS;
+SELECT $outsel FROM (
+ SELECT $outsel, ROWNUM $idx_name FROM (
+ SELECT $insel ${stripped_sql}${order_group_having}
+ ) $qalias
+) $qalias WHERE $idx_name BETWEEN ? AND ?
EOS
}
-
- return $sql;
}
-# used by _Top and _FetchFirst
+# used by _Top and _FetchFirst below
sub _prep_for_skimming_limit {
my ( $self, $sql, $rs_attrs ) = @_;
- # mangle the input sql as we will be replacing the selector
- $sql =~ s/^ \s* SELECT \s+ .+? \s+ (?= \b FROM \b )//ix
- or $self->throw_exception("Unrecognizable SELECT: $sql");
-
- my %r = ( inner_sql => $sql );
-
# get selectors
- my ($alias_map, $extra_order_sel);
- ($r{in_sel}, $r{out_sel}, $alias_map, $extra_order_sel)
- = $self->_subqueried_limit_attrs ($rs_attrs);
+ my (%r, $alias_map, $extra_order_sel);
+ ($r{inner_sql}, $r{in_sel}, $r{out_sel}, $alias_map, $extra_order_sel)
+ = $self->_subqueried_limit_attrs ($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
{
$r{mid_sel} .= ', ' . $extra_order_sel->{$extra_col};
}
- # since whatever order bindvals there are, they will be realiased
- # and need to show up in front of the entire initial inner subquery
- # *unshift* the selector bind stack to make this happen (horrible,
- # horrible, but we don't have another mechanism yet)
- unshift @{$self->{select_bind}}, @{$self->{order_bind}};
+ # Whatever order bindvals there are, they will be realiased and
+ # need to show up in front of the entire initial inner subquery
+ 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
my $root_rsrc = $rs_attrs->{_rsroot_rsrc};
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 $self->throw_exception("Unrecognizable SELECT: $sql");
-
- my ($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 $inf = $root_rsrc->storage->_resolve_column_info (
- $rs_attrs->{from}, [$order_by, $unq_sort_col]
- );
+ my ($first_ord_alias, $first_ord_col) = $first_order_by =~ /^ (?: ([^\.]+) \. )? ([^\.]+) $/x;
- 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 ($in_sel, $out_sel, $alias_map, $extra_order_sel)
- = $self->_subqueried_limit_attrs ($rs_attrs);
+ my ($stripped_sql, $in_sel, $out_sel, $alias_map, $extra_order_sel)
+ = $self->_subqueried_limit_attrs ($sql, $rs_attrs);
my $cmp_op = $direction eq 'desc' ? '>' : '<';
my $count_tbl_alias = 'rownum__emulation';
# 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,
+ my $rownum_cond;
+ if ($offset) {
+ $rownum_cond = 'BETWEEN ? AND ?';
+
+ push @{$self->{limit_bind}},
+ [ $self->__offset_bindtype => $offset ],
+ [ $self->__total_bindtype => $offset + $rows - 1]
+ ;
+ }
+ else {
+ $rownum_cond = '< ?';
+
+ push @{$self->{limit_bind}},
+ [ $self->__rows_bindtype => $rows ]
+ ;
+ }
+
+ return sprintf ("
SELECT $out_sel
FROM (
- SELECT $in_sel ${sql}${group_having_sql}
+ SELECT $in_sel ${stripped_sql}${group_having_sql}
) %s
-WHERE ( SELECT COUNT(*) FROM %s %s WHERE %s $cmp_op %s ) %s
+WHERE ( SELECT COUNT(*) FROM %s %s WHERE %s $cmp_op %s ) $rownum_cond
$order_sql
-EOS
- ( map { $self->_quote ($_) } (
- $rs_attrs->{alias},
- $root_tbl_name,
- $count_tbl_alias,
- "$count_tbl_alias.$unq_sort_col",
- $order_by,
- )),
- $offset
- ? do {
- push @{$self->{limit_bind}},
- [ $self->__offset_bindtype => $offset ], [ $self->__total_bindtype => $offset + $rows - 1];
- 'BETWEEN ? AND ?';
- }
- : do {
- push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ];
- '< ?';
- }
- ,
- );
-
- return $sql;
+ ", map { $self->_quote ($_) } (
+ $rs_attrs->{alias},
+ $root_tbl_name,
+ $count_tbl_alias,
+ "$count_tbl_alias.$first_ord_col",
+ "$first_ord_alias.$first_ord_col",
+ ));
}
# turned into a column alias (otherwise names in subqueries clash
# and/or lose their source table)
#
-# Returns inner/outer strings of SQL QUOTED selectors with aliases
-# (to be used in whatever select statement), and an alias index hashref
-# of QUOTED SEL => QUOTED ALIAS pairs (to maybe be used for string-subst
-# higher up).
+# Returns mangled proto-sql, inner/outer strings of SQL QUOTED selectors
+# with aliases (to be used in whatever select statement), and an alias
+# index hashref of QUOTED SEL => QUOTED ALIAS pairs (to maybe be used
+# for string-subst higher up).
# If an order_by is supplied, the inner select needs to bring out columns
# used in implicit (non-selected) orders, and the order condition itself
# needs to be realiased to the proper names in the outer query. Thus we
# QUOTED ALIAS pairs, which is a list of extra selectors that do *not*
# exist in the original select list
sub _subqueried_limit_attrs {
- my ($self, $rs_attrs) = @_;
+ my ($self, $proto_sql, $rs_attrs) = @_;
$self->throw_exception(
'Limit dialect implementation usable only in the context of DBIC (missing $rs_attrs)'
) unless ref ($rs_attrs) eq 'HASH';
+ # mangle the input sql as we will be replacing the selector entirely
+ unless (
+ $rs_attrs->{_selector_sql}
+ and
+ $proto_sql =~ s/^ \s* SELECT \s* \Q$rs_attrs->{_selector_sql}//ix
+ ) {
+ $self->throw_exception("Unrecognizable SELECT: $proto_sql");
+ }
+
my ($re_sep, $re_alias) = map { quotemeta $_ } ( $self->{name_sep}, $rs_attrs->{alias} );
+ # insulate from the multiple _recurse_fields calls below
+ local $self->{select_bind};
+
# correlate select and as, build selection index
my (@sel, $in_sel_index);
for my $i (0 .. $#{$rs_attrs->{select}}) {
push @sel, {
sql => $sql_sel,
- unquoted_sql => do { local $self->{quote_char}; $self->_recurse_fields ($s) },
+ unquoted_sql => do {
+ local $self->{quote_char};
+ $self->_recurse_fields ($s);
+ },
as =>
$sql_alias
||
push @out_sel, $self->_quote ($node->{as});
}
}
-
# see if the order gives us anything
my %extra_order_sel;
for my $chunk ($self->_order_by_chunks ($rs_attrs->{order_by})) {
}
return (
+ $proto_sql,
(map { join (', ', @$_ ) } (
\@in_sel,
\@out_sel)
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