查找并纠正外键违规行为

如需检查缺少相应主键的外键，请运行以下命令：

代码示例

  WITH q AS (
      SELECT conrelid::regclass AS fk_table, 
            confrelid::regclass AS pk_table, 
            format('(%s)',(select string_agg(format('fk.%I', attname), ', ') 
                FROM pg_attribute a 
                JOIN unnest(conkey) ia(nr) ON ia.nr = a.attnum
              WHERE attrelid = conrelid)) AS fk_fields, 
            format('(%s)',(select string_agg(format('pk.%I', attname), ', ') 
                FROM pg_attribute a 
                JOIN unnest(confkey) ia(nr) ON ia.nr = a.attnum
              WHERE attrelid = confrelid)) AS pk_fields, 
            pg_get_constraintdef(oid)
        FROM pg_constraint
      WHERE contype='f'
  )
  SELECT format(
  $sql$
  DO $$ BEGIN RAISE NOTICE 'checking Foreign Key %3$s%1$s ==> %4$s%2$s'; END;$$;
  SELECT %1$s, %2$s 
    FROM %3$s AS fk
    LEFT JOIN %4$s AS pk ON %1$s = %2$s 
    WHERE %2$s IS NULL
      AND  %1$s IS NOT NULL  /* any NULL on FK side bypasses FK constraint by design */
  /* use limit for testing, or detecting that "there is a problem in this table */
  --  LIMIT 10
  $sql$, fk_fields, pk_fields, fk_table, pk_table
  )
    FROM q
  \gexec
  

该脚本的输出将如下所示。如果没有输出，则表示没有违规行为，并且您已成功重新构建索引。

输出

  id | pk_id 
  ----+-------
      |     4
  (1 row)
  

在上述输出中，第一列显示主键列（在此示例中是名为 id 的列）。第二列是外键的引用列。这意味着存在 pk_id=4 行，其父主键不存在。您可以确定这些键是否有效，如果无效，则可以删除。