Issue #1079762 by mradcliffe, bzrudi71, alexpott, daffie, ogi:...

Issue #1079762 by mradcliffe, bzrudi71, alexpott, daffie, ogi: DatabaseSchema_pgsql::queryTableInformation() is slow

core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php

@@ -38,6 +38,13 @@ class Schema extends DatabaseSchema {
    */
   protected $maxIdentifierLength;
 
+  /**
+   * PostgreSQL's temporary namespace name.
+   *
+   * @var string
+   */
+  protected $tempNamespaceName;
+
   /**
    * Make sure to limit identifiers according to PostgreSQL compiled in length.
    *
@@ -97,38 +104,36 @@ public function queryTableInformation($table) {
       $key = 'public.' . $key;
     }
     else {
-      $schema = $this->connection->query('SELECT nspname FROM pg_namespace WHERE oid = pg_my_temp_schema()')->fetchField();
-      $key = $schema . '.' . $key;
+      $key = $this->getTempNamespaceName() . '.' . $key;
     }
 
     if (!isset($this->tableInformation[$key])) {
-      // Split the key into schema and table for querying.
-      list($schema, $table_name) = explode('.', $key);
       $table_information = (object) array(
         'blob_fields' => array(),
         'sequences' => array(),
       );
-      // Don't use {} around information_schema.columns table.
       $this->connection->addSavepoint();
 
       try {
-        // Check if the table information exists in the PostgreSQL metadata.
-        $table_information_exists = (bool) $this->connection->query("SELECT 1 FROM pg_class WHERE relname = :table", array(':table' => $table_name))->fetchField();
-
-        // If the table information does not yet exist in the PostgreSQL
-        // metadata, then return the default table information here, so that it
-        // will not be cached.
-        if (!$table_information_exists) {
-          $this->connection->releaseSavepoint();
-          return $table_information;
-        }
-        else {
-          $result = $this->connection->query("SELECT column_name, data_type, column_default FROM information_schema.columns WHERE table_schema = :schema AND table_name = :table AND (data_type = 'bytea' OR (numeric_precision IS NOT NULL AND column_default LIKE :default))", array(
-            ':schema' => $schema,
-            ':table' => $table_name,
-            ':default' => '%nextval%',
-          ));
-        }
+        // The bytea columns and sequences for a table can be found in
+        // pg_attribute, which is significantly faster than querying the
+        // information_schema. The data type of a field can be found by lookup
+        // of the attribute ID, and the default value must be extracted from the
+        // node tree for the attribute definition instead of the historical
+        // human-readable column, adsrc.
+        $sql = <<<'EOD'
+SELECT pg_attribute.attname AS column_name, format_type(pg_attribute.atttypid, pg_attribute.atttypmod) AS data_type, pg_get_expr(pg_attrdef.adbin, pg_attribute.attrelid) AS column_default
+FROM pg_attribute
+LEFT JOIN pg_attrdef ON pg_attrdef.adrelid = pg_attribute.attrelid AND pg_attrdef.adnum = pg_attribute.attnum
+WHERE pg_attribute.attnum > 0
+AND NOT pg_attribute.attisdropped
+AND pg_attribute.attrelid = :key::regclass
+AND (format_type(pg_attribute.atttypid, pg_attribute.atttypmod) = 'bytea'
+OR pg_attrdef.adsrc LIKE 'nextval%')
+EOD;
+        $result = $this->connection->query($sql, [
+          ':key' => $key,
+        ]);
       }
       catch (\Exception $e) {
         $this->connection->rollbackSavepoint();
@@ -136,6 +141,13 @@ public function queryTableInformation($table) {
       }
       $this->connection->releaseSavepoint();
 
+      // If the table information does not yet exist in the PostgreSQL
+      // metadata, then return the default table information here, so that it
+      // will not be cached.
+      if (empty($result)) {
+        return $table_information;
+      }
+
       foreach ($result as $column) {
         if ($column->data_type == 'bytea') {
           $table_information->blob_fields[$column->column_name] = TRUE;
@@ -153,6 +165,19 @@ public function queryTableInformation($table) {
     return $this->tableInformation[$key];
   }
 
+  /**
+   * Gets PostgreSQL's temporary namespace name.
+   *
+   * @return string
+   *   PostgreSQL's temporary namespace name.
+   */
+  protected function getTempNamespaceName() {
+    if (!isset($this->tempNamespaceName)) {
+      $this->tempNamespaceName = $this->connection->query('SELECT nspname FROM pg_namespace WHERE oid = pg_my_temp_schema()')->fetchField();
+    }
+    return $this->tempNamespaceName;
+  }
+
   /**
    * Resets information about table blobs, sequences and serial fields.
    *