Added option to output directed graphs of the group heirarchy before and after compression (#43)

It outputs nodes and edges information before and after the
compressor has run - these can be visualised in a tool like Gephi

A good way to visualise what the compressor is actually doing!

src/lib.rs

@@ -16,6 +16,10 @@
 //! Synapse instance's database. Specifically, it aims to reduce the number of
 //! rows that a given room takes up in the `state_groups_state` table.
 
+// This file contains configuring config options, which neccessarily means lots
+// of arguments - this hopefully doesn't make the code unclear
+// #[allow(clippy::too_many_arguments)] is therefore used around some functions
+
 use pyo3::{exceptions, prelude::*};
 
 #[cfg(feature = "jemalloc")]
@@ -31,6 +35,7 @@ use string_cache::DefaultAtom as Atom;
 
 mod compressor;
 mod database;
+mod graphing;
 
 use compressor::Compressor;
 use database::PGEscape;
@@ -72,6 +77,7 @@ pub struct Config {
     min_saved_rows: Option<i32>,
     transactions: bool,
     level_sizes: LevelSizes,
+    graphs: bool,
 }
 
 impl Config {
@@ -137,6 +143,10 @@ impl Config {
                 ))
                 .default_value("100,50,25")
                 .takes_value(true),
+        ).arg(
+            Arg::with_name("graphs")
+                .short("g")
+                .help("Whether to produce graphs of state groups before and after compression instead of SQL")
         ).get_matches();
 
         let db_url = matches
@@ -164,6 +174,8 @@ impl Config {
         let level_sizes = value_t!(matches, "level_sizes", LevelSizes)
             .unwrap_or_else(|e| panic!("Unable to parse level_sizes: {}", e));
 
+        let graphs = matches.is_present("graphs");
+
         Config {
             db_url: String::from(db_url),
             output_file,
@@ -172,6 +184,7 @@ impl Config {
             min_saved_rows,
             transactions,
             level_sizes,
+            graphs,
         }
     }
 }
@@ -260,6 +273,10 @@ pub fn run(mut config: Config) {
     // transaction.
 
     output_sql(&mut config, &state_group_map, &new_state_group_map);
+
+    if config.graphs {
+        graphing::make_graphs(state_group_map, new_state_group_map);
+    }
 }
 
 /// Produces SQL code to carry out changes and saves it to file
@@ -440,6 +457,7 @@ impl Config {
     /// Converts string and bool arguments into a Config struct
     ///
     /// This function panics if db_url or room_id are empty strings!
+    #[allow(clippy::too_many_arguments)]
     pub fn new(
         db_url: String,
         room_id: String,
@@ -448,6 +466,7 @@ impl Config {
         min_saved_rows: Option<i32>,
         transactions: bool,
         level_sizes: String,
+        graphs: bool,
     ) -> Result<Config, String> {
         let mut output: Option<File> = None;
         if let Some(file) = output_file {
@@ -471,6 +490,7 @@ impl Config {
             min_saved_rows,
             transactions,
             level_sizes,
+            graphs,
         })
     }
 }
@@ -480,6 +500,7 @@ impl Config {
 /// Default arguments are equivalent to using the command line tool
 /// No default's are provided for db_url or room_id since these arguments
 /// are compulsory (so that new() act's like parse_arguments())
+#[allow(clippy::too_many_arguments)]
 #[pyfunction(
     // db_url has no default
     // room_id  has no default
@@ -487,7 +508,8 @@ impl Config {
     max_state_group = "None",
     min_saved_rows = "None",
     transactions = false,
-    level_sizes = "String::from(\"100,50,25\")"
+    level_sizes = "String::from(\"100,50,25\")",
+    graphs = false
 )]
 fn run_compression(
     db_url: String,
@@ -497,6 +519,7 @@ fn run_compression(
     min_saved_rows: Option<i32>,
     transactions: bool,
     level_sizes: String,
+    graphs: bool,
 ) -> PyResult<()> {
     let config = Config::new(
         db_url,
@@ -506,6 +529,7 @@ fn run_compression(
         min_saved_rows,
         transactions,
         level_sizes,
+        graphs,
     );
     match config {
         Err(e) => Err(PyErr::new::<exceptions::PyException, _>(e)),