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Introduce logical decoding.

Browse Source 
This feature, building on previous commits, allows the write-ahead log
stream to be decoded into a series of logical changes; that is,
inserts, updates, and deletes and the transactions which contain them.
It is capable of handling decoding even across changes to the schema
of the effected tables.  The output format is controlled by a
so-called "output plugin"; an example is included.  To make use of
this in a real replication system, the output plugin will need to be
modified to produce output in the format appropriate to that system,
and to perform filtering.

Currently, information can be extracted from the logical decoding
system only via SQL; future commits will add the ability to stream
changes via walsender.

Andres Freund, with review and other contributions from many other
people, including Álvaro Herrera, Abhijit Menon-Sen, Peter Gheogegan,
Kevin Grittner, Robert Haas, Heikki Linnakangas, Fujii Masao, Abhijit
Menon-Sen, Michael Paquier, Simon Riggs, Craig Ringer, and Steve
Singer.
This commit is contained in:
Robert Haas
2014-03-03 16:32:18 -05:00
parent de94b47c0a
commit b89e151054
89 changed files with 12998 additions and 194 deletions
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98
src/backend/replication/slotfuncs.c
View File

@@ -15,13 +15,13 @@
#include "funcapi.h"
#include "miscadmin.h"
#include "access/htup_details.h"
#include "replication/slot.h"
#include "replication/logical.h"
#include "replication/logicalfuncs.h"
#include "utils/builtins.h"
#include "utils/pg_lsn.h"
#include "replication/slot.h"
Datum pg_create_physical_replication_slot(PG_FUNCTION_ARGS);
Datum pg_drop_replication_slot(PG_FUNCTION_ARGS);
static void
check_permissions(void)
@@ -54,7 +54,7 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
elog(ERROR, "return type must be a row type");
/* acquire replication slot, this will check for conflicting names*/
ReplicationSlotCreate(NameStr(*name), false);
ReplicationSlotCreate(NameStr(*name), false, RS_PERSISTENT);
values[0] = NameGetDatum(&MyReplicationSlot->data.name);
@@ -69,6 +69,68 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
PG_RETURN_DATUM(result);
}
/*
* SQL function for creating a new logical replication slot.
*/
Datum
pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
{
Name name = PG_GETARG_NAME(0);
Name plugin = PG_GETARG_NAME(1);
LogicalDecodingContext *ctx = NULL;
TupleDesc tupdesc;
HeapTuple tuple;
Datum result;
Datum values[2];
bool nulls[2];
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
check_permissions();
CheckLogicalDecodingRequirements();
Assert(!MyReplicationSlot);
/*
* Acquire a logical decoding slot, this will check for conflicting
* names.
*/
ReplicationSlotCreate(NameStr(*name), true, RS_EPHEMERAL);
/*
* Create logical decoding context, to build the initial snapshot.
*/
ctx = CreateInitDecodingContext(
NameStr(*plugin), NIL,
logical_read_local_xlog_page, NULL, NULL);
/* build initial snapshot, might take a while */
DecodingContextFindStartpoint(ctx);
values[0] = CStringGetTextDatum(NameStr(MyReplicationSlot->data.name));
values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
/* don't need the decoding context anymore */
FreeDecodingContext(ctx);
memset(nulls, 0, sizeof(nulls));
tuple = heap_form_tuple(tupdesc, values, nulls);
result = HeapTupleGetDatum(tuple);
/* ok, slot is now fully created, mark it as persistent */
ReplicationSlotPersist();
ReplicationSlotRelease();
PG_RETURN_DATUM(result);
}
/*
* SQL function for dropping a replication slot.
*/
@@ -92,7 +154,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
Datum
pg_get_replication_slots(PG_FUNCTION_ARGS)
{
#define PG_STAT_GET_REPLICATION_SLOTS_COLS 6
#define PG_GET_REPLICATION_SLOTS_COLS 8
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
@@ -134,15 +196,16 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
for (slotno = 0; slotno < max_replication_slots; slotno++)
{
ReplicationSlot *slot = &ReplicationSlotCtl->replication_slots[slotno];
Datum values[PG_STAT_GET_REPLICATION_SLOTS_COLS];
bool nulls[PG_STAT_GET_REPLICATION_SLOTS_COLS];
Datum values[PG_GET_REPLICATION_SLOTS_COLS];
bool nulls[PG_GET_REPLICATION_SLOTS_COLS];
TransactionId xmin;
TransactionId catalog_xmin;
XLogRecPtr restart_lsn;
bool active;
Oid database;
NameData slot_name;
NameData plugin;
int i;
SpinLockAcquire(&slot->mutex);
@@ -154,9 +217,11 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
else
{
xmin = slot->data.xmin;
catalog_xmin = slot->data.catalog_xmin;
database = slot->data.database;
restart_lsn = slot->data.restart_lsn;
namecpy(&slot_name, &slot->data.name);
namecpy(&plugin, &slot->data.plugin);
active = slot->active;
}
@@ -166,19 +231,34 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
i = 0;
values[i++] = NameGetDatum(&slot_name);
if (database == InvalidOid)
nulls[i++] = true;
else
values[i++] = NameGetDatum(&plugin);
if (database == InvalidOid)
values[i++] = CStringGetTextDatum("physical");
else
values[i++] = CStringGetTextDatum("logical");
if (database == InvalidOid)
nulls[i++] = true;
else
values[i++] = database;
values[i++] = BoolGetDatum(active);
if (xmin != InvalidTransactionId)
values[i++] = TransactionIdGetDatum(xmin);
else
nulls[i++] = true;
if (catalog_xmin != InvalidTransactionId)
values[i++] = TransactionIdGetDatum(catalog_xmin);
else
nulls[i++] = true;
if (restart_lsn != InvalidTransactionId)
values[i++] = LSNGetDatum(restart_lsn);
else