Update README.md

Author: bartnv

README.md

@@ -1,7 +1,7 @@
 # xml-to-postgres
 A fast tool to convert XML files with repeating element sets into PostgreSQL dump format.
 
-To use this tool you need to create a simple YAML configuration file that describes how to turn repeating element sets in an XML document into row-based data for importing into PostgreSQL. For efficiency, the data is output in PostgreSQL dump format, suitable for importing with the COPY command. This tool processes one row at a time and does not need to keep the whole XML DOM in memory, so it has a very low memory footprint and can be used to convert datasets much larger than the available RAM. The tool can split out further repeating fields into extra tables with a one-to-many relationship (with foreign key) to the main table.
+To use this tool you need to create a simple YAML configuration file that describes how to turn repeating element sets in an XML document into row-based data for importing into PostgreSQL. For efficiency, the data is output in PostgreSQL dump format, suitable for importing with the COPY command. This tool processes one row at a time and does not need to keep the whole XML DOM in memory, so it has a very low memory footprint and can be used to convert datasets larger than the available RAM. The tool can split out further repeating fields into extra tables with a one-to-many relationship (with foreign key) to the main table.
 
 ## Features
 
@@ -11,3 +11,36 @@ To use this tool you need to create a simple YAML configuration file that descri
  * Apply search-and-replace on values
  * Filter the output with regex
  * Write extra tables with a foreign key to the main table
+ * Operate in a pipeline to avoid on-disk intermediary steps
+
+## Compiling
+
+This project uses the Rust 2021 Edition, which means you need at a minimum to have the Rust 1.56 toolchain installed. The project uses only stable features and will only add dependencies that can compile on stable. It's a normal Rust project managed by Cargo, so you can compile with this simple command:
+
+    cargo build --release
+
+The debug build really hurts performance, so unless you're doing a deep dive in the code it is recommended to compile for release.
+
+## Running
+
+Basic usage:
+
+    xml-to-postgres <config.yml> [data.xml]
+
+So the YAML configuration file is a required argument. The XML input file can be passed in as the second argument or can be sent to stdin if omitted.
+
+Example invocation:
+
+    xml-to-postgres config.yml data.xml > data.dump
+
+Within a pipeline:
+
+    unzip -p xml.zip | xml-to-postgres config.yml | psql <database> -c '\copy <table> from stdin'
+
+Within a database transaction:
+
+    xml-to-postgres config.yml data.xml | psql <database> -c 'BEGIN' -c 'TRUNCATE <table>' -c '\copy <table> from stdin' -c 'COMMIT'
+
+## Configuration
+
+See [documentation for the configuration file](https://github.com/bartnv/xml-to-postgres/wiki/Configuration-options) in the wiki.