git.m6w6.name Git - mdref/mdref-pq-gateway/blob - Relations.md

   1 # class pq\Gateway\Table\Relations implements Countable, IteratorAggregate
   2
   3 Retrieve any relations referenced by the table through foreign keys.
   4 See pq\Gateway\Table::by() and pq\Gateway\Table::with().
   5
   6 ## Query:
   7
   8 The following query is executed by the current executor of the table to retrieve the table references:
   9
  10         select
  11                  case when att1.attname like '%\_'||att2.attname then
  12                         substring(att1.attname from '^.*(?=_'||att2.attname||'$)')
  13                  else
  14                         att1.attname
  15                  end          as "id"
  16                 ,cl1.relname  as "foreignTable"
  17                 ,att1.attname as "foreignColumn"
  18                 ,cl2.relname  as "referencedTable"
  19                 ,att2.attname as "referencedColumn"
  20         from
  21                  pg_constraint co
  22                 ,pg_class      cl1
  23                 ,pg_class      cl2
  24                 ,pg_attribute  att1
  25                 ,pg_attribute  att2
  26         where
  27                 (       cl1.relname = \$1
  28                 or      cl2.relname = \$1)
  29         and co.confrelid != 0
  30         and co.conrelid   = cl1.oid
  31         and co.conkey[1]  = att1.attnum and cl1.oid = att1.attrelid
  32         and co.confrelid  = cl2.oid
  33         and co.confkey[1] = att2.attnum and cl2.oid = att2.attrelid
  34         order by
  35                  cl1.relname
  36                 ,att1.attnum
  37
  38 ## Cache:
  39
  40 The result of this query is cached in the metadata cache under the following key, where $table is converted to a string by pq\Gateway\Table::__toString():
  41
  42         "$table:relations"
  43
  44 ## Foreign key access:
  45
  46 Relations can be accessed as virtual properties or through pq\Gateway\Table\Relations::getReference().
  47
  48         <?php
  49
  50         use pq\Gateway\Table;
  51
  52         $relations = new Table\Relations(new Table("account_email"));
  53
  54         // $relations->reference->account
  55         $account_rel = $relations->getReference("account");
  56         $account_rel = $relations->account;
  57
  58         ?>
  59
  60 > ***NOTE:***
  61   The relation name is the column name of the foreign key with the column name of the referenced column cut off the end.
  62
  63 ## Properties:
  64
  65 * protected array $references
  66   The table's foreign keys.
  67