Add PostgreSQL Support (#3)

Reviewed-on: #3

src/Query/Definition.php

@@ -2,7 +2,7 @@
 
 namespace BitBadger\PDODocument\Query;
 
-use BitBadger\PDODocument\{Configuration, DocumentException, Mode};
+use BitBadger\PDODocument\{Configuration, DocumentException, DocumentIndex, Mode};
 
 /**
  * Queries to define tables and indexes
@@ -68,4 +68,25 @@ class Definition
     {
         return str_replace('INDEX', 'UNIQUE INDEX', self::ensureIndexOn($tableName, 'key', [Configuration::$idField]));
     }
+
+    /**
+     * Create a document-wide index on a table (PostgreSQL only)
+     *
+     * @param string $tableName The name of the table on which the document index should be created
+     * @param DocumentIndex $indexType The type of index to be created
+     * @return string The SQL statement to create an index on JSON documents in the specified table
+     * @throws DocumentException If the database mode is not PostgreSQL
+     */
+    public static function ensureDocumentIndexOn(string $tableName, DocumentIndex $indexType): string
+    {
+        if (Configuration::$mode <> Mode::PgSQL) {
+            throw new DocumentException('Document indexes are only supported on PostgreSQL');
+        }
+        [, $tbl]  = self::splitSchemaAndTable($tableName);
+        $extraOps = match ($indexType) {
+            DocumentIndex::Full => '',
+            DocumentIndex::Optimized => ' jsonb_path_ops'
+        };
+        return "CREATE INDEX IF NOT EXISTS idx_{$tbl}_document ON $tableName USING GIN (data$extraOps)";
+    }
 }