Update README

Author: ololobus

README.md

@@ -4,7 +4,7 @@
 
 ## Overview
 
-Ptrack is a fast block-level incremental backup engine for PostgreSQL. Currently `ptrack` codebase is split approximately 50/50% between PostgreSQL core patch and extension. All public SQL API methods are placed in the `ptrack` extension, while the main engine is still in core.
+Ptrack is a fast block-level incremental backup engine for PostgreSQL. Currently `ptrack` codebase is split between small PostgreSQL core patch and extension. All public SQL API methods and main engine are placed in the `ptrack` extension, while the core patch contains only certain hooks and modifies binary utilities to ignore `ptrack.map.*` files.
 
 ## Installation
 
@@ -17,15 +17,16 @@ git clone https://github.com/postgres/postgres.git -b REL_12_STABLE && cd postgr
 2) Apply PostgreSQL core patch:
 
 ```shell
-git apply ptrack/patches/ptrack-2.0-core.diff
+git apply -3 ptrack/patches/REL_12_STABLE-ptrack-core.diff
 ```
 
 3) Compile and install PostgreSQL
 
-4) Set `ptrack_map_size` (in MB)
+4) Set `ptrack.map_size` (in MB)
 
 ```shell
-echo 'ptrack_map_size = 64' >> postgres_data/postgresql.conf
+echo "shared_preload_libraries = 'ptrack'" >> postgres_data/postgresql.conf
+echo "ptrack.map_size = 64" >> postgres_data/postgresql.conf
 ```
 
 5) Compile and install `ptrack` extension
@@ -42,10 +43,9 @@ CREATE EXTENSION ptrack;
 
 ## Public SQL API
 
- * ptrack_version() --- returns ptrack version string (2.0 currently).
- * pg_ptrack_get_pagemapset('LSN') --- returns a set of changed data files with bitmaps of changed blocks since specified LSN.
- * pg_ptrack_control_lsn() --- returns LSN of the last ptrack map initialization.
- * pg_ptrack_get_block --- returns a requested block of relation.
+ * ptrack_version() — returns ptrack version string (2.0 currently).
+ * ptrack_get_pagemapset('LSN') — returns a set of changed data files with bitmaps of changed blocks since specified LSN.
+ * ptrack_init_lsn() — returns LSN of the last ptrack map initialization.
 
 ## Architecture