Ptrack 2.0 initial release

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.

Credits to:

* Konstantin Knizhnik
* Anastasia Lubennikova
* Alexey Kondratov

.gitignore

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+.deps
+*.so
+*.o
+ptrack--2.0.sql
+

LICENSE

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+ptrack is released under the PostgreSQL License, a liberal Open Source license, similar to the BSD or MIT licenses.
+
+Copyright (c) 2015-2020, Postgres Professional
+Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
+Portions Copyright (c) 1994, The Regents of the University of California
+
+Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies.
+
+IN NO EVENT SHALL POSTGRES PROFESSIONAL BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF POSTGRES PROFESSIONAL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+POSTGRES PROFESSIONAL SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND POSTGRES PROFESSIONAL HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

Makefile

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+# contrib/ptrack/Makefile
+
+MODULE_big = ptrack
+OBJS = ptrack.o $(WIN32RES)
+EXTENSION = ptrack
+EXTVERSION = 2.0
+DATA = ptrack.sql
+DATA_built = $(EXTENSION)--$(EXTVERSION).sql
+PGFILEDESC = "ptrack - public API for internal ptrack engine"
+
+EXTRA_CLEAN = $(EXTENSION)--$(EXTVERSION).sql
+
+ifdef USE_PGXS
+PG_CONFIG ?= pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/ptrack
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
+
+$(EXTENSION)--$(EXTVERSION).sql: ptrack.sql
+	cat $^ > $@
+
+temp-install: EXTRA_INSTALL=contrib/ptrack

README.md

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+# ptrack
+
+## 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.
+
+## Installation
+
+1) Apply PostgreSQL core patch:
+
+```shell
+git apply patches/ptrack-2.0-core.diff
+```
+
+2) Compile and install PostgreSQL
+
+3) Set `ptrack_map_size` (in MB)
+
+```shell
+echo 'ptrack_map_size = 64' >> postgres_data/postgresql.conf
+```
+
+4) Compile and install `ptrack` extension
+
+```shell
+USE_PGXS=1 make -C /path/to/ptrack/ install
+```
+
+5) Run PostgreSQL and create `ptrack` extension
+
+```sql
+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.
+
+## Architecture
+
+TBA
+
+## Roadmap
+
+The main goal currently is to move as much `ptrack` functionality into the extension as possible and leave only certain requred hooks as core patch.