90 lines
2.6 KiB
C
90 lines
2.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* message.c
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* Generic logical messages.
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*
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* Copyright (c) 2013-2023, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/backend/replication/logical/message.c
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*
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* NOTES
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*
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* Generic logical messages allow XLOG logging of arbitrary binary blobs that
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* get passed to the logical decoding plugin. In normal XLOG processing they
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* are same as NOOP.
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*
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* These messages can be either transactional or non-transactional.
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* Transactional messages are part of current transaction and will be sent to
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* decoding plugin using in a same way as DML operations.
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* Non-transactional messages are sent to the plugin at the time when the
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* logical decoding reads them from XLOG. This also means that transactional
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* messages won't be delivered if the transaction was rolled back but the
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* non-transactional one will always be delivered.
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*
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* Every message carries prefix to avoid conflicts between different decoding
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* plugins. The plugin authors must take extra care to use unique prefix,
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* good options seems to be for example to use the name of the extension.
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*
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* ---------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/xact.h"
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#include "access/xloginsert.h"
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#include "miscadmin.h"
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#include "nodes/execnodes.h"
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#include "replication/logical.h"
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#include "replication/message.h"
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#include "utils/memutils.h"
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/*
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* Write logical decoding message into XLog.
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*/
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XLogRecPtr
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LogLogicalMessage(const char *prefix, const char *message, size_t size,
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bool transactional)
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{
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xl_logical_message xlrec;
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/*
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* Force xid to be allocated if we're emitting a transactional message.
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*/
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if (transactional)
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{
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Assert(IsTransactionState());
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GetCurrentTransactionId();
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}
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xlrec.dbId = MyDatabaseId;
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xlrec.transactional = transactional;
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/* trailing zero is critical; see logicalmsg_desc */
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xlrec.prefix_size = strlen(prefix) + 1;
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xlrec.message_size = size;
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XLogBeginInsert();
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XLogRegisterData((char *) &xlrec, SizeOfLogicalMessage);
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XLogRegisterData(unconstify(char *, prefix), xlrec.prefix_size);
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XLogRegisterData(unconstify(char *, message), size);
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/* allow origin filtering */
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XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
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return XLogInsert(RM_LOGICALMSG_ID, XLOG_LOGICAL_MESSAGE);
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}
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/*
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* Redo is basically just noop for logical decoding messages.
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*/
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void
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logicalmsg_redo(XLogReaderState *record)
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{
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uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
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if (info != XLOG_LOGICAL_MESSAGE)
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elog(PANIC, "logicalmsg_redo: unknown op code %u", info);
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/* This is only interesting for logical decoding, see decode.c. */
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}
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