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When implementing a replication solution ontop of logical decoding, two related problems exist: * How to safely keep track of replication progress * How to change replication behavior, based on the origin of a row; e.g. to avoid loops in bi-directional replication setups The solution to these problems, as implemented here, consist out of three parts: 1) 'replication origins', which identify nodes in a replication setup. 2) 'replication progress tracking', which remembers, for each replication origin, how far replay has progressed in a efficient and crash safe manner. 3) The ability to filter out changes performed on the behest of a replication origin during logical decoding; this allows complex replication topologies. E.g. by filtering all replayed changes out. Most of this could also be implemented in "userspace", e.g. by inserting additional rows contain origin information, but that ends up being much less efficient and more complicated. We don't want to require various replication solutions to reimplement logic for this independently. The infrastructure is intended to be generic enough to be reusable. This infrastructure also replaces the 'nodeid' infrastructure of commit timestamps. It is intended to provide all the former capabilities, except that there's only 2^16 different origins; but now they integrate with logical decoding. Additionally more functionality is accessible via SQL. Since the commit timestamp infrastructure has also been introduced in 9.5 (commit 73c986add) changing the API is not a problem. For now the number of origins for which the replication progress can be tracked simultaneously is determined by the max_replication_slots GUC. That GUC is not a perfect match to configure this, but there doesn't seem to be sufficient reason to introduce a separate new one. Bumps both catversion and wal page magic. Author: Andres Freund, with contributions from Petr Jelinek and Craig Ringer Reviewed-By: Heikki Linnakangas, Petr Jelinek, Robert Haas, Steve Singer Discussion: 20150216002155.GI15326@awork2.anarazel.de, 20140923182422.GA15776@alap3.anarazel.de, 20131114172632.GE7522@alap2.anarazel.de
107 lines
2.9 KiB
C
107 lines
2.9 KiB
C
/*-------------------------------------------------------------------------
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* output_plugin.h
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* PostgreSQL Logical Decode Plugin Interface
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*
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* Copyright (c) 2012-2015, PostgreSQL Global Development Group
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef OUTPUT_PLUGIN_H
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#define OUTPUT_PLUGIN_H
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#include "replication/reorderbuffer.h"
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struct LogicalDecodingContext;
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struct OutputPluginCallbacks;
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typedef enum OutputPluginOutputType
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{
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OUTPUT_PLUGIN_BINARY_OUTPUT,
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OUTPUT_PLUGIN_TEXTUAL_OUTPUT
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} OutputPluginOutputType;
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/*
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* Options set by the output plugin, in the startup callback.
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*/
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typedef struct OutputPluginOptions
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{
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OutputPluginOutputType output_type;
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} OutputPluginOptions;
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/*
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* Type of the shared library symbol _PG_output_plugin_init that is looked up
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* when loading an output plugin shared library.
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*/
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typedef void (*LogicalOutputPluginInit) (struct OutputPluginCallbacks *cb);
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/*
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* Callback that gets called in a user-defined plugin. ctx->private_data can
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* be set to some private data.
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*
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* "is_init" will be set to "true" if the decoding slot just got defined. When
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* the same slot is used from there one, it will be "false".
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*/
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typedef void (*LogicalDecodeStartupCB) (
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struct LogicalDecodingContext *ctx,
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OutputPluginOptions *options,
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bool is_init
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);
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/*
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* Callback called for every (explicit or implicit) BEGIN of a successful
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* transaction.
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*/
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typedef void (*LogicalDecodeBeginCB) (
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struct LogicalDecodingContext *,
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ReorderBufferTXN *txn);
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/*
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* Callback for every individual change in a successful transaction.
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*/
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typedef void (*LogicalDecodeChangeCB) (
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struct LogicalDecodingContext *,
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ReorderBufferTXN *txn,
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Relation relation,
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ReorderBufferChange *change
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);
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/*
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* Called for every (explicit or implicit) COMMIT of a successful transaction.
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*/
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typedef void (*LogicalDecodeCommitCB) (
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struct LogicalDecodingContext *,
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ReorderBufferTXN *txn,
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XLogRecPtr commit_lsn);
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/*
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* Filter changes by origin.
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*/
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typedef bool (*LogicalDecodeFilterByOriginCB) (
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struct LogicalDecodingContext *,
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RepOriginId origin_id);
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/*
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* Called to shutdown an output plugin.
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*/
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typedef void (*LogicalDecodeShutdownCB) (
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struct LogicalDecodingContext *
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);
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/*
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* Output plugin callbacks
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*/
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typedef struct OutputPluginCallbacks
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{
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LogicalDecodeStartupCB startup_cb;
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LogicalDecodeBeginCB begin_cb;
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LogicalDecodeChangeCB change_cb;
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LogicalDecodeCommitCB commit_cb;
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LogicalDecodeFilterByOriginCB filter_by_origin_cb;
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LogicalDecodeShutdownCB shutdown_cb;
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} OutputPluginCallbacks;
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void OutputPluginPrepareWrite(struct LogicalDecodingContext *ctx, bool last_write);
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void OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write);
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#endif /* OUTPUT_PLUGIN_H */
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