MODULE_big = pg_dtm

OBJS = pg_dtm.o

EXTENSION = pg_dtm

DATA = pg_dtm--1.0.sql

ifndef PG_CONFIG

PG_CONFIG = pg_config

PGXS := $(shell $(PG_CONFIG) --pgxs)

include $(PGXS)

===

dtm

===

Distributed transaction management tools for PostgreSQL.

--------------------

Communication scheme

--------------------

.- Backend -.

/ \

/ \

DTM ---- Backend ---- Coordinator

\ /

\ /

`- Backend -´

-----------------------

Coordinator-Backend API

-----------------------

This API includes a set of postgres procedures that

the coordinator can call with "select" statement.

extend_transaction (n integer) -> (higcid gcid)

join_transaction (higcid gcid) -> ()

FIXME: add procedures that would start and finish 2pc

----------

libdtm api

----------

typedef unsigned long long cid_t;

// Connects to the specified DTM.

DTMConn DtmConnect(char *host, int port);

// Disconnects from the DTM. Do not use the 'dtm' pointer after this call, or

// bad things will happen.

void DtmDisconnect(DTMConn dtm);

// Asks DTM for the first 'gcid' with unknown status. This 'gcid' is used as a

// kind of snapshot. Returns the 'gcid' on success, or INVALID_GCID otherwise.

cid_t DtmGlobalGetNextCid(DTMConn dtm);

// Prepares a commit. Returns the 'gcid' on success, or INVALID_GCID otherwise.

cid_t DtmGlobalPrepare(DTMConn dtm);

// Finishes a given commit with 'committed' status. Returns 'true' on success,

// 'false' otherwise.

bool DtmGlobalCommit(DTMConn dtm, cid_t gcid);

// Finishes a given commit with 'aborted' status.

void DtmGlobalRollback(DTMConn dtm, cid_t gcid);

// Gets the status of the commit identified by 'gcid'. Returns the status on

// success, or -1 otherwise.

int DtmGlobalGetTransStatus(DTMConn dtm, cid_t gcid);

--------------------

Backend-DTM Protocol

--------------------

DTM <--> Backend:

<- 'p'<hex16 self> - "prepare"

-> '+'<hex16 gcid> - "commit prepared"

-> '-' - "something went wrong"

<- 'c'<hex16 gcid> - "commit"

-> '+' - "commit saved"

-> '-' - "something went wrong"

<- 'a'<hex16 gcid> - "abort"

-> '+' - "abort saved"

-> '-' - "something went wrong"

<- 'h' - "horizon"

-> '+'<hex16 gcid> - "here is a gcid you can use as a snapshot"

-> '-' - "something went wrong"

<- 's'<hex16 gcid> - "status"

-> '+''c|a|?' - "here is the transaction status"

(c)ommitted, (a)borted or (?)unknown

-> '-' - "something went wrong"

Backend disconnection is considered as an abort of all incomplete commits

prepared by that backend.

\echo Use "CREATE EXTENSION pg_dtm" to load this file. \quit

CREATE FUNCTION dtm_extend(gtid cstring default null) RETURNS bigint

AS 'MODULE_PATHNAME','dtm_extend'

LANGUAGE C;

CREATE FUNCTION dtm_access(snapshot bigint, gtid cstring default null) RETURNS bigint

AS 'MODULE_PATHNAME','dtm_access'

LANGUAGE C;

CREATE FUNCTION dtm_begin_prepare(gtid cstring) RETURNS void

AS 'MODULE_PATHNAME','dtm_begin_prepare'

LANGUAGE C;

CREATE FUNCTION dtm_prepare(gtid cstring, csn bigint) RETURNS bigint

AS 'MODULE_PATHNAME','dtm_prepare'

LANGUAGE C;

CREATE FUNCTION dtm_end_prepare(gtid cstring, csn bigint) RETURNS void

AS 'MODULE_PATHNAME','dtm_end_prepare'

LANGUAGE C;