pg_meta_data
(PHP 4 >= 4.3.0, PHP 5)
pg_meta_data — Get meta data for table
Описание
array pg_meta_data
( resource $connection
, string $table_name
)
pg_meta_data() returns table definition for table_name as an array.
Внимание
Эта функция является ЭКСПЕРИМЕНТАЛЬНОЙ. Поведение этой функции, ее имя и относящаяся к ней документация могут измениться в последующих версиях PHP без уведомления. Используйте эту функцию на свой страх и риск.
Список параметров
- connection
-
PostgreSQL database connection resource.
- table_name
-
The name of the table.
Возвращаемые значения
An array of the table definition, or FALSE on error.
Примеры
Пример #1 Getting table metadata
<?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>';
}
?>
Результат выполнения данного примера:
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) } }
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Коментарии
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($dbconn,'drop table foo');
Throws an error:
pg_exec(): Query failed: ERROR: table "foo" does not exist in ...
You can get some possibly more useful information with the query:
SELECT table_name, column_name, data_type, character_maximum_length FROM information_schema.columns WHERE table_name='tablename';
The built in function does not provide any support for selecting a schema. If you need schema support and do not want to alter your SEARCH_PATH, the following function can provide it:
function meta_data($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;
}
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);
}
?>
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)
?>