1 2=head1 NAME 3 4Tangram::Sucks - what there is to be improved in Tangram 5 6=head1 DESCRIPTION 7 8Tangram has taken a concept very familiar to programmers in Java land 9to its logical completion. 10 11This document is an attempt by the coders of Tangram to summarise the 12major problems that are inherant in the design, describe cases for 13which the Tangram metaphor does not work well, and list long standing 14TO-DO items. 15 16=head2 DESIGN CAVEATS 17 18=over 19 20=item B<query language does not cover all SQL expressions> 21 22Whilst there is no underlying fault with the query object metaphor 23I<per se>, there are currently lots of queries that cannot be 24expressed in current versions of Tangram, and adding new parts to the 25language is not easy. 26 27=item B<some loss of encapsulation with queries> 28 29It could be said this is not a problem. After all, adding properties 30to a schema of an object is akin to declaring them as "public". 31 32Some people banter on about I<data access patterns>, which the Tangram 33schema represents. But OO terms like that are usually treated as 34buzzwords anyway. 35 36=back 37 38=head2 HARD PROBLEMS 39 40=over 41 42=item B<partial column select> 43 44This optimisation has some serious dangers associated with it. 45 46It could either be 47 48=item B<no support for SQL UPDATE> 49 50It may be possible to write a version of C<$storage-E<gt>select()> 51that does this, which would look something like: 52 53 $storage->update 54 ( $r_object, 55 set => [ $r_object->{bar} == $r_object->{baz} + 2 ], 56 filter => ($r_object->{frop} != undef) 57 ); 58 59=item B<no explicit support for re-orgs> 60 61The situation where you have a large amount of schema reshaping to do, 62with a complex enough data structure can turn into a fairly difficult 63problem. 64 65It is possible to have two Tangram stores with different schema and 66simply load objects from one and put them in the other - however the 67on-demand autoloading combined with the automatic insertion of unknown 68objects will result in the entire database being loaded into core if 69it is sufficiently interlinked. 70 71=item B<replace SQL expression core> 72 73The whole SQL expression core needs to be replaced with a SQL 74abstraction module that is a little better planned. For instance, 75there should be placeholders used in a lot more places where the code 76just sticks in an integer etc. 77 78=item B<support for `large' collections> 79 80Where it is impractical or undesirable to load all of a collection 81into memory, when you are adding a member and then updating the 82container, it should be possible to do this without loading the 83entire collection into memory. 84 85This could actually be achieved with a new Tangram::Type. 86 87=back 88 89=head2 MISSING FEATURES 90 91=over 92 93=item B<concise query expressions> 94 95For simple selects, the query syntax is too long. Getting remote 96objects should take less code. 97 98=item B<non-ID joins> 99 100We can't join on anything but "ID" values 101 102=item B<tables with no primary key> 103 104We can't map tables unless they have a primary key, and it is called 105"id" (or, at least, the same name as the rest of the schema). 106 107=item B<tables with multi-column primary keys> 108 109We can't map tables when they have multiple primary keys. Well, you 110can, but only if you make a view with an ID column which is 111functionally derived from the multi-part keys. But that sucks. 112 113=item B<tables with auto_increment keys> 114 115These suck, but Tangram could still support them without requiring 116schema hacks. 117 118=item B<tables without a `type' column> 119 120The 'type' column is unneeded for base tables which do not have 121sub-classes. 122 123=item B<tables with custom `type' columns> 124 125For mapping schemata where some clever person has invented their own 126special way of representing types using discrete column values. 127 128=item B<tables with implicit (presence) `type' columns> 129 130It should be possible to infer the type value based on knowledge of 131the schema, and the tables which have rows. 132 133=item B<fully symmetric relationships> 134 135back-refs are read-only. 136 137=item B<bulk inserts> 138 139Inserting lots of similar objects should be more efficient. Right now 140it generates a new DBI statement handler for each object. 141 142=item B<`empty subclass' schema support> 143 144You should not need to explicitly add new classes to a schema if a 145superclass of them is already in the schema. 146 147=item B<warn about column redefinitions> 148 149Defining a column twice should be an error. Reported by Mark 150Lawrence. 151 152=back 153 154 155=cut 156 157