pg_meta_data()

(PHP 4 >= 4.3.0, PHP 5, PHP 7)

获得表的元数据

说明

pg_meta_data(resource $connection,string $table_name): array

pg_metadata()以数组形式返回table_name表的定义。

Warning

此函数是实验性的。此函数的表象，包括名称及其相关文档都可能在未来的PHP 发布版本中未通知就被修改。使用本函数风险自担。

参数

$connection

PostgreSQL database connection resource.

$table_name

The name of the table.

返回值

以数组array形式返回表的定义，如果出错则返回FALSE。

范例

Example #1 取得表的元数据

<?php
  $dbconn = pg_connect("dbname=publisher") or die("Could not connect");
  $meta = pg_meta_data($dbconn, 'authors');
  if (is_array($meta)) {
      echo '<pre>';
      var_dump($meta);
      echo '</pre>';
  }
?>

以上例程会输出：

array(3) {
["author"]=>
array(5) {
  ["num"]=>
  int(1)
  ["type"]=>
  string(7) "varchar"
  ["len"]=>
  int(-1)
  ["not null"]=>
  bool(false)
  ["has default"]=>
  bool(false)
}
["year"]=>
array(5) {
  ["num"]=>
  int(2)
  ["type"]=>
  string(4) "int2"
  ["len"]=>
  int(2)
  ["not null"]=>
  bool(false)
  ["has default"]=>
  bool(false)
}
["title"]=>
array(5) {
  ["num"]=>
  int(3)
  ["type"]=>
  string(7) "varchar"
  ["len"]=>
  int(-1)
  ["not null"]=>
  bool(false)
  ["has default"]=>
  bool(false)
}
}

参见

• pg_convert()将关联的数组值转换为适合 SQL 语句的格式。

You can get some possibly more useful information with the query:
SELECT table_name, column_name, data_type, character_maximum_length FROM information_schema.columns WHERE table_name='tablename';

If parameter $extended not false:
<?php
array (size=2)
 'name' => 
  array (size=11)
   'num' => int 1
   'type' => string 'varchar' (length=7)
   'len' => int -1
   'not null' => boolean false
   'has default' => boolean true
   'array dims' => int 0
   'is enum' => boolean false
   'is base' => boolean true
   'is composite' => boolean false
   'is pesudo' => boolean false
   'description' => string '' (length=0)
 'id' => 
  array (size=11)
   'num' => int 2
   'type' => string 'int4' (length=4)
   'len' => int 4
   'not null' => boolean true
   'has default' => boolean true
   'array dims' => int 0
   'is enum' => boolean false
   'is base' => boolean true
   'is composite' => boolean false
   'is pesudo' => boolean false
   'description' => string '' (length=0)
?>

To specify a schema as well as a table name, use the "schemaname.tablename" form as usual for PostgreSQL and the other functions in this extension. Without the prefix, of course, the default schema search path is used.
<?php
 $meta = pg_meta_data($dbconn, 'foo.bar'); // table "bar" in schema "foo"
 if (is_array($meta)) {
   var_dump($meta);
 }
?>

This function seems to be case-sensitive on tablename (php-4.3.1)
The Array returned is of the following structure
['field name'] => Array
  (
   ['num'] => Field number starting at 1
   ['type'] => data type, eg varchar, int4
   ['len'] => internal storage size of field. -1 for varying
   ['not null'] => boolean
   ['has default'] => boolean
  )
   ......
for Varied size datatypes (varchar, text, etc) 
you can get the max data length from the system table pg_attribute.atttypmod -4
eg. 
select attnum, attname , atttypmod -4 as field_len 
from pg_attribute, pg_class 
where relname='$tablename' 
and attrelid=relfilenode 
and attnum>=1

When querying on meta data from a temp table, the meta data seems to persist even if a fresh connection is established, where the temp table no longer exists.
 For example, if you create a connection and a temp table like so:
$dbconn1 = pg_connect('blah blah', , PGSQL_CONNECT_FORCE_NEW);
pg_exec($dbconn1,'create temp table foo as select 'foo' as namecol, 'bar' as valcol');
Then create a new connection
$dbconn2 = pg_connect('blah blah', , PGSQL_CONNECT_FORCE_NEW);
And query the meta data for table 'foo' in this new connection, it will report the facts about this table:
pg_meta_data($dbconn2,'foo');
"'Array ( [foo] => Array ( [num] => 1 [type] => varchar... "
However, trying to remove this table:
pg_exec($dbconn,'drop table foo');
Throws an error:
pg_exec(): Query failed: ERROR: table "foo" does not exist in ...

The built in function does not provide any support for selecting a schema. If you need schema support and do not want to alter your SEARCH_PATH, the following function can provide it:
 function meta_data($table, $schema = 'public')
  {
$result = pg_query_params("SELECT a.attname, a.attnum, t.typname, a.attlen, a.attnotNULL, a.atthasdef, a.attndims 
FROM pg_class as c, pg_attribute a, pg_type t, pg_namespace n
WHERE a.attnum > 0 
AND a.attrelid = c.oid 
AND c.relname = $1
AND a.atttypid = t.oid 
AND n.oid = c.relnamespace
AND n.nspname = $2
ORDER BY a.attnum", array($table, $schema));
$fields = array();
while($row = pg_fetch_array()) {
$fields['attname'] = $row;
} 
    return $fields;
  }