Avoid an expensive attachment counting query on the post editing screen. See #27985, for trunk.

git-svn-id: https://develop.svn.wordpress.org/trunk@28191 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/post.php

@@ -2291,6 +2291,23 @@ function wp_count_attachments( $mime_type = '' ) {
 	return apply_filters( 'wp_count_attachments', (object) $counts, $mime_type );
 }
 
+/**
+ * Determine if at least one attachment of a particular mime-type has been uploaded
+ *
+ * @global wpdb $wpdb
+ *
+ * @since 3.9.1
+ *
+ * @param string $mime_type The mime-type string to check.
+ *
+ * @return int|null If exist, the post ID of the first found attachment.
+ */
+function wp_has_mime_type_attachments( $mime_type ) {
+	global $wpdb;
+	$sql = sprintf( "SELECT ID FROM $wpdb->posts WHERE post_type = 'attachment' AND post_mime_type LIKE '%s%%' LIMIT 1", like_escape( $mime_type ) );
+	return $wpdb->get_var( $sql );
+}
+
 /**
  * Get default post mime types
  *