X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FStorage%2FDBI%2FMSSQL.pm;h=d9c8ee0442fd4fc7018275150cf75cba982b92b9;hb=6d766626a066b757058d023830f93cf39bb9c302;hp=cddfc5e9e444a968df5abf0f133c65bf3fdbfa57;hpb=b8d88d9b31a7bf9b755cc8b396d5c47cb5bcf3fb;p=dbsrgits%2FDBIx-Class.git diff --git a/lib/DBIx/Class/Storage/DBI/MSSQL.pm b/lib/DBIx/Class/Storage/DBI/MSSQL.pm index cddfc5e..d9c8ee0 100644 --- a/lib/DBIx/Class/Storage/DBI/MSSQL.pm +++ b/lib/DBIx/Class/Storage/DBI/MSSQL.pm @@ -3,7 +3,7 @@ package DBIx::Class::Storage::DBI::MSSQL; use strict; use warnings; -use base qw/DBIx::Class::Storage::DBI::AmbiguousGlob DBIx::Class::Storage::DBI/; +use base qw/DBIx::Class::Storage::DBI::UniqueIdentifier/; use mro 'c3'; use List::Util(); @@ -66,43 +66,12 @@ sub insert_bulk { } } -# support MSSQL GUID column types - sub insert { my $self = shift; my ($source, $to_insert) = @_; my $supplied_col_info = $self->_resolve_column_info($source, [keys %$to_insert] ); - my %guid_cols; - my @pk_cols = $source->primary_columns; - my %pk_cols; - @pk_cols{@pk_cols} = (); - - my @pk_guids = grep { - $source->column_info($_)->{data_type} - && - $source->column_info($_)->{data_type} =~ /^uniqueidentifier/i - } @pk_cols; - - my @auto_guids = grep { - $source->column_info($_)->{data_type} - && - $source->column_info($_)->{data_type} =~ /^uniqueidentifier/i - && - $source->column_info($_)->{auto_nextval} - } grep { not exists $pk_cols{$_} } $source->columns; - - my @get_guids_for = - grep { not exists $to_insert->{$_} } (@pk_guids, @auto_guids); - - my $updated_cols = {}; - - for my $guid_col (@get_guids_for) { - my ($new_guid) = $self->_get_dbh->selectrow_array('SELECT NEWID()'); - $updated_cols->{$guid_col} = $to_insert->{$guid_col} = $new_guid; - } - my $is_identity_insert = (List::Util::first { $_->{is_auto_increment} } (values %$supplied_col_info) ) ? 1 : 0; @@ -111,13 +80,12 @@ sub insert { $self->_set_identity_insert ($source->name); } - $updated_cols = { %$updated_cols, %{ $self->next::method(@_) } }; + my $updated_cols = $self->next::method(@_); if ($is_identity_insert) { $self->_unset_identity_insert ($source->name); } - return $updated_cols; } @@ -179,8 +147,9 @@ sub _execute { sub last_insert_id { shift->_identity } # -# MSSQL is retarded wrt ordered subselects. One needs to add a TOP 100% -# to *all* subqueries, do it here. +# MSSQL is retarded wrt ordered subselects. One needs to add a TOP +# to *all* subqueries, but one also can't use TOP 100 PERCENT +# http://sqladvice.com/forums/permalink/18496/22931/ShowThread.aspx#22931 # sub _select_args_to_query { my $self = shift; @@ -189,8 +158,12 @@ sub _select_args_to_query { # see if this is an ordered subquery my $attrs = $_[3]; - if ( scalar $self->sql_maker->_order_by_chunks ($attrs->{order_by}) ) { - $sql =~ s/^ \s* SELECT \s/SELECT TOP 100 PERCENT /xi; + if ( scalar $self->_parse_order_by ($attrs->{order_by}) ) { + $self->throw_exception( + 'An ordered subselect encountered - this is not safe! Please see "Ordered Subselects" in DBIx::Class::Storage::DBI::MSSQL + ') unless $attrs->{unsafe_subselect_ok}; + my $max = 2 ** 32; + $sql =~ s/^ \s* SELECT \s/SELECT TOP $max /xi; } return wantarray @@ -227,14 +200,39 @@ sub build_datetime_parser { sub sqlt_type { 'SQLServer' } -sub _sql_maker_opts { - my ( $self, $opts ) = @_; +sub sql_maker { + my $self = shift; + + unless ($self->_sql_maker) { + unless ($self->{_sql_maker_opts}{limit_dialect}) { + + my $version = $self->_server_info->{normalized_dbms_version} || 0; + + $self->{_sql_maker_opts} = { + limit_dialect => ($version >= 9 ? 'RowNumberOver' : 'Top'), + %{$self->{_sql_maker_opts}||{}} + }; + } - if ( $opts ) { - $self->{_sql_maker_opts} = { %$opts }; + my $maker = $self->next::method (@_); } - return { limit_dialect => 'RowNumberOver', %{$self->{_sql_maker_opts}||{}} }; + return $self->_sql_maker; +} + +sub _ping { + my $self = shift; + + my $dbh = $self->_dbh or return 0; + + local $dbh->{RaiseError} = 1; + local $dbh->{PrintError} = 0; + + eval { + $dbh->do('select 1'); + }; + + return $@ ? 0 : 1; } 1; @@ -282,9 +280,57 @@ $table_name ON>. Unfortunately this operation in MSSQL requires the C privilege, which is normally not included in the standard write-permissions. +=head2 Ordered Subselects + +If you attempted the following query (among many others) in Microsoft SQL +Server + + $rs->search ({}, { + prefetch => 'relation', + rows => 2, + offset => 3, + }); + +You may be surprised to receive an exception. The reason for this is a quirk +in the MSSQL engine itself, and sadly doesn't have a sensible workaround due +to the way DBIC is built. DBIC can do truly wonderful things with the aid of +subselects, and does so automatically when necessary. The list of situations +when a subselect is necessary is long and still changes often, so it can not +be exhaustively enumerated here. The general rule of thumb is a joined +L relationship with limit/group +applied to the left part of the join. + +In its "pursuit of standards" Microsft SQL Server goes to great lengths to +forbid the use of ordered subselects. This breaks a very useful group of +searches like "Give me things number 4 to 6 (ordered by name), and prefetch +all their relations, no matter how many". While there is a hack which fools +the syntax checker, the optimizer may B. +Testing has determined that while such breakage does occur (the test suite +contains an explicit test which demonstrates the problem), it is relative +rare. The benefits of ordered subselects are on the other hand too great to be +outright disabled for MSSQL. + +Thus compromise between usability and perfection is the MSSQL-specific +L C. +It is deliberately not possible to set this on the Storage level, as the user +should inspect (and preferably regression-test) the return of every such +ResultSet individually. The example above would work if written like: + + $rs->search ({}, { + unsafe_subselect_ok => 1, + prefetch => 'relation', + rows => 2, + offset => 3, + }); + +If it is possible to rewrite the search() in a way that will avoid the need +for this flag - you are urged to do so. If DBIC internals insist that an +ordered subselect is necessary for an operation, and you believe there is a +different/better way to get the same result - please file a bugreport. + =head1 AUTHOR -See L. +See L and L. =head1 LICENSE