diff -u b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php
--- b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php
+++ b/core/modules/pgsql/src/Driver/Database/pgsql/Connection.php
@@ -95,11 +95,12 @@
     assert(is_string($prefix), 'The \'$prefix\' argument to ' . __METHOD__ . '() must be a string');
     $this->prefix = $prefix;
 
-    // Add the schema name of it is not set to public, else it will use the
+    // Add the schema name if it is not set to public, otherwise it will use the
     // default schema name.
     $quoted_schema = '';
-    if (isset($this->connectionOptions['schema']) && ($this->connectionOptions['schema'] != 'public')) {
-      $quoted_schema = $this->identifierQuotes[0] . $this->connectionOptions['schema'] . $this->identifierQuotes[1] . '.';
+    if (isset($this->connectionOptions['schema']) && ($this->connectionOptions['schema'] !== 'public')) {
+      $sanitizedSchema = preg_replace('/[^A-Za-z0-9_]+/', '', $this->connectionOptions['schema']);
+      $quoted_schema = $this->identifierQuotes[0] . $sanitizedSchema . $this->identifierQuotes[1] . '.';
     }
 
     $this->tablePlaceholderReplacements = [
diff -u b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php
--- b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php
+++ b/core/modules/pgsql/src/Driver/Database/pgsql/Schema.php
@@ -56,9 +56,10 @@
   public function __construct($connection) {
     parent::__construct($connection);
 
-    // If the schema is not set in the connection options than schema defaults
+    // If the schema is not set in the connection options then schema defaults
     // to public.
     $this->defaultSchema = $connection->getConnectionOptions()['schema'] ?? 'public';
+    $this->defaultSchema = preg_replace('/[^A-Za-z0-9_]+/', '', $this->defaultSchema);
   }
 
   /**
@@ -128,6 +129,7 @@
   public function queryTableInformation($table) {
     // Generate a key to reference this table's information on.
     $prefixed_table = $this->connection->getPrefix() . $table;
+    $key = $this->connection->prefixTables('{' . $table . '}');
 
     // Take into account that temporary tables are stored in a different schema.
     // \Drupal\Core\Database\Connection::generateTemporaryTableName() sets the
@@ -136,12 +138,8 @@
       $key = $quoted_key = $this->getTempNamespaceName() . '.' . $prefixed_table;
     }
-    elseif ($this->defaultSchema != 'public') {
+    else {
       $key = $this->defaultSchema . '.' . $prefixed_table;
       $quoted_key = '"' . $this->defaultSchema . '"."' . $prefixed_table . '"';
     }
-    else {
-      $key = $this->defaultSchema . '.' . $prefixed_table;
-      $quoted_key = '"' . $prefixed_table . '"';
-    }
 
     if (!isset($this->tableInformation[$key])) {
@@ -723,7 +721,6 @@
     // clause and not used as an identifier.
     $index_name = str_replace('"', '', $index_name);
 
-    // Get the schema and tablename for the old table.
     $sql_params = [
       ':schema' => $this->defaultSchema,
       ':table' => $this->connection->getPrefix() . $table,