resolves #1346 (#1347)

Author: qrort

ydb/library/yql/tools/mrrun/README.md

@@ -0,0 +1,34 @@
+# mrrun - Utility for MR query debugging
+
+`mrrun` is a utility designed for local debugging of MapReduce queries. It allows you to execute YQL programs which involve creation of YT transactions.
+
+## Command-Line Options
+
+- `-p <file>`: _(required)_ specify a file with an SQL query or an s-expression (`-` for /dev/stdin).
+- `-s`: if specified, SQL is used; if not specified, the query plan execution specified in s-expression is used.
+- `-f <alias>@<path>`: attach a local file to the query
+- `--mrjob-bin <path>`: specify the path of mrjob binary to upload (the mrrun itself is used by default)
+
+## Example of Local Usage
+
+```bash
+mrrun -s -p query.sql -f file.txt@./some-file.txt
+```
+
+In this example, `mrrun` will use SQL from the file `query.sql`, with file `./some-file.txt` attached to the request with alias `file.txt`.
+
+The simple example of `query.sql`:
+
+```sql
+USE `hahn`;
+
+SELECT Length(name) FROM `home/yql/tutorial/users`;
+SELECT FileContent('file.txt');
+```
+## mrjob binary
+
+Note that default mrjob binary (mrrun itself) has size of ~2GB, so it will take a long time to upload it to YT.
+It is recommended to compile mrjob separately and strip it (final size is about 200MB), then pass it to the dedicated command-line parameter.
+```bash``
+mrrun -s -p query.sql --mrjob-bin ./ydb/library/yql/tools/mrjob/mrjob
+```