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Add option to enable two_phase commits via pg_create_logical_replication_slot.

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Commit 0aa8a01d04 extends the output plugin API to allow decoding of
prepared xacts and allowed the user to enable/disable the two-phase option
via pg_logical_slot_get_changes(). This can lead to a problem such that
the first time when it gets changes via pg_logical_slot_get_changes()
without two_phase option enabled it will not get the prepared even though
prepare is after consistent snapshot. Now next time during getting changes,
if the two_phase option is enabled it can skip prepare because by that
time start decoding point has been moved. So the user will only get commit
prepared.

Allow to enable/disable this option at the create slot time and default
will be false. It will break the existing slots which is fine in a major
release.

Author: Ajin Cherian
Reviewed-by: Amit Kapila and Vignesh C
Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
This commit is contained in:
Amit Kapila
2021-03-03 07:28:43 +05:30
parent ee28cacf61
commit 19890a064e
20 changed files with 131 additions and 93 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
src/backend/replication/logical/logical.c
View File

@@ -431,6 +431,12 @@ CreateInitDecodingContext(const char *plugin,
startup_cb_wrapper(ctx, &ctx->options, true);
MemoryContextSwitchTo(old_context);
/*
* We allow decoding of prepared transactions iff the two_phase option is
* enabled at the time of slot creation.
*/
ctx->twophase &= MyReplicationSlot->data.two_phase;
ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
return ctx;
@@ -531,6 +537,12 @@ CreateDecodingContext(XLogRecPtr start_lsn,
startup_cb_wrapper(ctx, &ctx->options, false);
MemoryContextSwitchTo(old_context);
/*
* We allow decoding of prepared transactions iff the two_phase option is
* enabled at the time of slot creation.
*/
ctx->twophase &= MyReplicationSlot->data.two_phase;
ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
ereport(LOG,

10
src/backend/replication/slot.c
View File

@@ -216,10 +216,17 @@ ReplicationSlotValidateName(const char *name, int elevel)
* name: Name of the slot
* db_specific: logical decoding is db specific; if the slot is going to
* be used for that pass true, otherwise false.
* two_phase: Allows decoding of prepared transactions. We allow this option
* to be enabled only at the slot creation time. If we allow this option
* to be changed during decoding then it is quite possible that we skip
* prepare first time because this option was not enabled. Now next time
* during getting changes, if the two_phase option is enabled it can skip
* prepare because by that time start decoding point has been moved. So the
* user will only get commit prepared.
*/
void
ReplicationSlotCreate(const char *name, bool db_specific,
ReplicationSlotPersistency persistency)
ReplicationSlotPersistency persistency, bool two_phase)
{
ReplicationSlot *slot = NULL;
int i;
@@ -277,6 +284,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
namestrcpy(&slot->data.name, name);
slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
slot->data.persistency = persistency;
slot->data.two_phase = two_phase;
/* and then data only present in shared memory */
slot->just_dirtied = false;

14
src/backend/replication/slotfuncs.c
View File

@@ -50,7 +50,7 @@ create_physical_replication_slot(char *name, bool immediately_reserve,
/* acquire replication slot, this will check for conflicting names */
ReplicationSlotCreate(name, false,
temporary ? RS_TEMPORARY : RS_PERSISTENT);
temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
if (immediately_reserve)
{
@@ -124,7 +124,8 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
*/
static void
create_logical_replication_slot(char *name, char *plugin,
bool temporary, XLogRecPtr restart_lsn,
bool temporary, bool two_phase,
XLogRecPtr restart_lsn,
bool find_startpoint)
{
LogicalDecodingContext *ctx = NULL;
@@ -140,7 +141,7 @@ create_logical_replication_slot(char *name, char *plugin,
* error as well.
*/
ReplicationSlotCreate(name, true,
temporary ? RS_TEMPORARY : RS_EPHEMERAL);
temporary ? RS_TEMPORARY : RS_EPHEMERAL, two_phase);
/*
* Create logical decoding context to find start point or, if we don't
@@ -177,6 +178,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
Name name = PG_GETARG_NAME(0);
Name plugin = PG_GETARG_NAME(1);
bool temporary = PG_GETARG_BOOL(2);
bool two_phase = PG_GETARG_BOOL(3);
Datum result;
TupleDesc tupdesc;
HeapTuple tuple;
@@ -193,6 +195,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
create_logical_replication_slot(NameStr(*name),
NameStr(*plugin),
temporary,
two_phase,
InvalidXLogRecPtr,
true);
@@ -236,7 +239,7 @@ pg_drop_replication_slot(PG_FUNCTION_ARGS)
Datum
pg_get_replication_slots(PG_FUNCTION_ARGS)
{
#define PG_GET_REPLICATION_SLOTS_COLS 13
#define PG_GET_REPLICATION_SLOTS_COLS 14
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
@@ -432,6 +435,8 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
values[i++] = Int64GetDatum(failLSN - currlsn);
}
values[i++] = BoolGetDatum(slot_contents.data.two_phase);
Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
@@ -796,6 +801,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
create_logical_replication_slot(NameStr(*dst_name),
plugin,
temporary,
false,
src_restart_lsn,
false);
}

6
src/backend/replication/walsender.c
View File

@@ -938,7 +938,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
if (cmd->kind == REPLICATION_KIND_PHYSICAL)
{
ReplicationSlotCreate(cmd->slotname, false,
cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT);
cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
false);
}
else
{
@@ -952,7 +953,8 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
* they get dropped on error as well.
*/
ReplicationSlotCreate(cmd->slotname, true,
cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL);
cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
cmd->two_phase);
}
if (cmd->kind == REPLICATION_KIND_LOGICAL)