diff -r 25c1ff79297c -r 4fce579bed22 include/relpipe/writer/BufferingMode.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/include/relpipe/writer/BufferingMode.h	Sat Apr 23 23:23:29 2022 +0200
@@ -0,0 +1,62 @@
+/**
+ * Relational pipes (library)
+ * Copyright © 2022 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the:
+ *  - GNU Lesser General Public License as published by the Free Software Foundation;
+ *    version 3 of the License or (at your option)
+ *  - GNU General Public License as published by the Free Software Foundation;
+ *    version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+namespace relpipe {
+namespace writer {
+
+/**
+ * Relational output might be – and usually is – buffered
+ * i.e. relational data are written to a buffer and flushed later and sent to the actual output stream.
+ * 
+ * Through these modes we can control when the flush is done.
+ * 
+ * Recommendation:
+ *  - batch processing: AUTO
+ *  - interactive processing: RECORD
+ *  - tools should not set the mode explicitly unless asked by the user or unles specific mode is obvious for given task;
+ *    then ENVIRONMENT mode is the initial one and it defaults to AUTO when user has not set the environmental variable
+ */
+enum class BufferingMode {
+	/**
+	 * Output buffer is not explicitly flushed, it is written when full.
+	 */
+	AUTO,
+	/**
+	 * Mode is determined by the environmental variable RELPIPE_WRITER_BUFFERING_MODE.
+	 * If value is missing or has invalid value, AUTO is used as default.
+	 */
+	ENVIRONMENT,
+	/**
+	 * Output buffer is flushed at least at the end of each relation.
+	 */
+	RELATION,
+	/**
+	 * Output buffer is flushed at least at the end of each record.
+	 */
+	RECORD,
+	/**
+	 * Output buffer is flushed at least at the end of each attribute.
+	 */
+	ATTRIBUTE
+};
+
+}
+}