multiple primary keys for table "history" are not allowed

What database system is this? Everywhere I look 42P16 is a is a PostgreSQL error. If so you should be on 8.3 or higher.

Fixing version

Same error running PostgreSQL 9.3.13

Checking the key and it is created

SELECT a.attname, format_type(a.atttypid, a.atttypmod) AS data_type
FROM   pg_index i
JOIN   pg_attribute a ON a.attrelid = i.indrelid AND a.attnum = ANY(i.indkey)
WHERE  i.indrelid = 'drupal.history'::regclass AND    i.indisprimary;

attname | data_type 
---------+-----------
 uid     | integer
 nid     | bigint

If I drop the key ALTER TABLE drupal.history DROP CONSTRAINT history_pkey; I can create it using ALTER TABLE drupal.history ADD PRIMARY KEY (uid,nid);

Debugged some more, key gets never dropped, dropPrimaryKey checks if the constraint exists, but it fails.

public function dropPrimaryKey($table) {
    if (!$this->constraintExists($table, 'pkey')) {
      return FALSE;
    }

    $this->connection->query('ALTER TABLE {' . $table . '} DROP CONSTRAINT ' . $this->prefixNonTable($table, 'pkey'));
    return TRUE;
  }
}

but executing SELECT 1 FROM pg_constraint WHERE conname = 'history_pkey'; returns

 ?column? 
----------
        1
(1 row)

For some reason constraintExists($table, $name) uses {} around the table name, but this doesn't work if your table name is prefixed. So changing $constraint_name = '{' . $table . '}_' . $name; to $constraint_name = $table . '_' . $name;, solves it.

PS: Same for the indexes $index_name = '{' . $table . '}_' . $name . '_idx'; to $index_name = $table . '_' . $name . '_idx';

Based on #9 could this be related to #1009828: constraintExists doesn't work with multiple schemas (or is that something else)?

Not sure if it's the same, it links to #1008128: Do not use a single underscore as table and index separator on PostgreSQL and SQLite which does not have a real patch, and I'm not really a psql expert.

On this instance there's a prefix defined 'prefix' => 'drupal.',

I guess this belongs in the release notes at https://www.drupal.org/project/drupal/releases/7.50, so I took a stab at adding it to the "Known issues" section although I wasn't sure exactly what to write: https://www.drupal.org/node/2762447/revisions/view/9922761/9923859

This also happens on 7.44, tried installing the new version of panels and got the following error

Performed update: panelizer_update_7111                                     [ok]
Performed update: panelizer_update_7112                                     [ok]
SQLSTATE[42P16]: Invalid table definition: 7 ERROR:  multiple primary keys for table "panelizer_entity" are not allowed

Adding a patch to see what testbot says, it's add the 2 lines of #9 and #10

Reset issue status.

This problem was fixed in Drupal 7.89 release by #998898: Make sure that the identifiers are not more the 63 characters on PostgreSQL , where the DatabaseSchema_pgsql::constraintExists() function was changed. I am not able to simulate the problem anymore, even if I prefix the history table. Therefore I am closing this.