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Diffstat (limited to 'src/backend/replication/slotfuncs.c')
| -rw-r--r-- | src/backend/replication/slotfuncs.c | 916 |
1 files changed, 916 insertions, 0 deletions
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c new file mode 100644 index 0000000..16a3527 --- /dev/null +++ b/src/backend/replication/slotfuncs.c @@ -0,0 +1,916 @@ +/*------------------------------------------------------------------------- + * + * slotfuncs.c + * Support functions for replication slots + * + * Copyright (c) 2012-2022, PostgreSQL Global Development Group + * + * IDENTIFICATION + * src/backend/replication/slotfuncs.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "access/htup_details.h" +#include "access/xlog_internal.h" +#include "access/xlogrecovery.h" +#include "access/xlogutils.h" +#include "funcapi.h" +#include "miscadmin.h" +#include "replication/decode.h" +#include "replication/logical.h" +#include "replication/slot.h" +#include "utils/builtins.h" +#include "utils/inval.h" +#include "utils/pg_lsn.h" +#include "utils/resowner.h" + +/* + * Helper function for creating a new physical replication slot with + * given arguments. Note that this function doesn't release the created + * slot. + * + * If restart_lsn is a valid value, we use it without WAL reservation + * routine. So the caller must guarantee that WAL is available. + */ +static void +create_physical_replication_slot(char *name, bool immediately_reserve, + bool temporary, XLogRecPtr restart_lsn) +{ + Assert(!MyReplicationSlot); + + /* acquire replication slot, this will check for conflicting names */ + ReplicationSlotCreate(name, false, + temporary ? RS_TEMPORARY : RS_PERSISTENT, false); + + if (immediately_reserve) + { + /* Reserve WAL as the user asked for it */ + if (XLogRecPtrIsInvalid(restart_lsn)) + ReplicationSlotReserveWal(); + else + MyReplicationSlot->data.restart_lsn = restart_lsn; + + /* Write this slot to disk */ + ReplicationSlotMarkDirty(); + ReplicationSlotSave(); + } +} + +/* + * SQL function for creating a new physical (streaming replication) + * replication slot. + */ +Datum +pg_create_physical_replication_slot(PG_FUNCTION_ARGS) +{ + Name name = PG_GETARG_NAME(0); + bool immediately_reserve = PG_GETARG_BOOL(1); + bool temporary = PG_GETARG_BOOL(2); + Datum values[2]; + bool nulls[2]; + TupleDesc tupdesc; + HeapTuple tuple; + Datum result; + + if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE) + elog(ERROR, "return type must be a row type"); + + CheckSlotPermissions(); + + CheckSlotRequirements(); + + create_physical_replication_slot(NameStr(*name), + immediately_reserve, + temporary, + InvalidXLogRecPtr); + + values[0] = NameGetDatum(&MyReplicationSlot->data.name); + nulls[0] = false; + + if (immediately_reserve) + { + values[1] = LSNGetDatum(MyReplicationSlot->data.restart_lsn); + nulls[1] = false; + } + else + nulls[1] = true; + + tuple = heap_form_tuple(tupdesc, values, nulls); + result = HeapTupleGetDatum(tuple); + + ReplicationSlotRelease(); + + PG_RETURN_DATUM(result); +} + + +/* + * Helper function for creating a new logical replication slot with + * given arguments. Note that this function doesn't release the created + * slot. + * + * When find_startpoint is false, the slot's confirmed_flush is not set; it's + * caller's responsibility to ensure it's set to something sensible. + */ +static void +create_logical_replication_slot(char *name, char *plugin, + bool temporary, bool two_phase, + XLogRecPtr restart_lsn, + bool find_startpoint) +{ + LogicalDecodingContext *ctx = NULL; + + Assert(!MyReplicationSlot); + + /* + * Acquire a logical decoding slot, this will check for conflicting names. + * Initially create persistent slot as ephemeral - that allows us to + * nicely handle errors during initialization because it'll get dropped if + * this transaction fails. We'll make it persistent at the end. Temporary + * slots can be created as temporary from beginning as they get dropped on + * error as well. + */ + ReplicationSlotCreate(name, true, + temporary ? RS_TEMPORARY : RS_EPHEMERAL, two_phase); + + /* + * Create logical decoding context to find start point or, if we don't + * need it, to 1) bump slot's restart_lsn and xmin 2) check plugin sanity. + * + * Note: when !find_startpoint this is still important, because it's at + * this point that the output plugin is validated. + */ + ctx = CreateInitDecodingContext(plugin, NIL, + false, /* just catalogs is OK */ + restart_lsn, + XL_ROUTINE(.page_read = read_local_xlog_page, + .segment_open = wal_segment_open, + .segment_close = wal_segment_close), + NULL, NULL, NULL); + + /* + * If caller needs us to determine the decoding start point, do so now. + * This might take a while. + */ + if (find_startpoint) + DecodingContextFindStartpoint(ctx); + + /* don't need the decoding context anymore */ + FreeDecodingContext(ctx); +} + +/* + * 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); + bool temporary = PG_GETARG_BOOL(2); + bool two_phase = PG_GETARG_BOOL(3); + Datum result; + TupleDesc tupdesc; + HeapTuple tuple; + 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"); + + CheckSlotPermissions(); + + CheckLogicalDecodingRequirements(); + + create_logical_replication_slot(NameStr(*name), + NameStr(*plugin), + temporary, + two_phase, + InvalidXLogRecPtr, + true); + + values[0] = NameGetDatum(&MyReplicationSlot->data.name); + values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush); + + 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 if needed */ + if (!temporary) + ReplicationSlotPersist(); + ReplicationSlotRelease(); + + PG_RETURN_DATUM(result); +} + + +/* + * SQL function for dropping a replication slot. + */ +Datum +pg_drop_replication_slot(PG_FUNCTION_ARGS) +{ + Name name = PG_GETARG_NAME(0); + + CheckSlotPermissions(); + + CheckSlotRequirements(); + + ReplicationSlotDrop(NameStr(*name), true); + + PG_RETURN_VOID(); +} + +/* + * pg_get_replication_slots - SQL SRF showing active replication slots. + */ +Datum +pg_get_replication_slots(PG_FUNCTION_ARGS) +{ +#define PG_GET_REPLICATION_SLOTS_COLS 14 + ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo; + XLogRecPtr currlsn; + int slotno; + + /* + * We don't require any special permission to see this function's data + * because nothing should be sensitive. The most critical being the slot + * name, which shouldn't contain anything particularly sensitive. + */ + + InitMaterializedSRF(fcinfo, 0); + + currlsn = GetXLogWriteRecPtr(); + + LWLockAcquire(ReplicationSlotControlLock, LW_SHARED); + for (slotno = 0; slotno < max_replication_slots; slotno++) + { + ReplicationSlot *slot = &ReplicationSlotCtl->replication_slots[slotno]; + ReplicationSlot slot_contents; + Datum values[PG_GET_REPLICATION_SLOTS_COLS]; + bool nulls[PG_GET_REPLICATION_SLOTS_COLS]; + WALAvailability walstate; + int i; + + if (!slot->in_use) + continue; + + /* Copy slot contents while holding spinlock, then examine at leisure */ + SpinLockAcquire(&slot->mutex); + slot_contents = *slot; + SpinLockRelease(&slot->mutex); + + memset(values, 0, sizeof(values)); + memset(nulls, 0, sizeof(nulls)); + + i = 0; + values[i++] = NameGetDatum(&slot_contents.data.name); + + if (slot_contents.data.database == InvalidOid) + nulls[i++] = true; + else + values[i++] = NameGetDatum(&slot_contents.data.plugin); + + if (slot_contents.data.database == InvalidOid) + values[i++] = CStringGetTextDatum("physical"); + else + values[i++] = CStringGetTextDatum("logical"); + + if (slot_contents.data.database == InvalidOid) + nulls[i++] = true; + else + values[i++] = ObjectIdGetDatum(slot_contents.data.database); + + values[i++] = BoolGetDatum(slot_contents.data.persistency == RS_TEMPORARY); + values[i++] = BoolGetDatum(slot_contents.active_pid != 0); + + if (slot_contents.active_pid != 0) + values[i++] = Int32GetDatum(slot_contents.active_pid); + else + nulls[i++] = true; + + if (slot_contents.data.xmin != InvalidTransactionId) + values[i++] = TransactionIdGetDatum(slot_contents.data.xmin); + else + nulls[i++] = true; + + if (slot_contents.data.catalog_xmin != InvalidTransactionId) + values[i++] = TransactionIdGetDatum(slot_contents.data.catalog_xmin); + else + nulls[i++] = true; + + if (slot_contents.data.restart_lsn != InvalidXLogRecPtr) + values[i++] = LSNGetDatum(slot_contents.data.restart_lsn); + else + nulls[i++] = true; + + if (slot_contents.data.confirmed_flush != InvalidXLogRecPtr) + values[i++] = LSNGetDatum(slot_contents.data.confirmed_flush); + else + nulls[i++] = true; + + /* + * If invalidated_at is valid and restart_lsn is invalid, we know for + * certain that the slot has been invalidated. Otherwise, test + * availability from restart_lsn. + */ + if (XLogRecPtrIsInvalid(slot_contents.data.restart_lsn) && + !XLogRecPtrIsInvalid(slot_contents.data.invalidated_at)) + walstate = WALAVAIL_REMOVED; + else + walstate = GetWALAvailability(slot_contents.data.restart_lsn); + + switch (walstate) + { + case WALAVAIL_INVALID_LSN: + nulls[i++] = true; + break; + + case WALAVAIL_RESERVED: + values[i++] = CStringGetTextDatum("reserved"); + break; + + case WALAVAIL_EXTENDED: + values[i++] = CStringGetTextDatum("extended"); + break; + + case WALAVAIL_UNRESERVED: + values[i++] = CStringGetTextDatum("unreserved"); + break; + + case WALAVAIL_REMOVED: + + /* + * If we read the restart_lsn long enough ago, maybe that file + * has been removed by now. However, the walsender could have + * moved forward enough that it jumped to another file after + * we looked. If checkpointer signalled the process to + * termination, then it's definitely lost; but if a process is + * still alive, then "unreserved" seems more appropriate. + * + * If we do change it, save the state for safe_wal_size below. + */ + if (!XLogRecPtrIsInvalid(slot_contents.data.restart_lsn)) + { + int pid; + + SpinLockAcquire(&slot->mutex); + pid = slot->active_pid; + slot_contents.data.restart_lsn = slot->data.restart_lsn; + SpinLockRelease(&slot->mutex); + if (pid != 0) + { + values[i++] = CStringGetTextDatum("unreserved"); + walstate = WALAVAIL_UNRESERVED; + break; + } + } + values[i++] = CStringGetTextDatum("lost"); + break; + } + + /* + * safe_wal_size is only computed for slots that have not been lost, + * and only if there's a configured maximum size. + */ + if (walstate == WALAVAIL_REMOVED || max_slot_wal_keep_size_mb < 0) + nulls[i++] = true; + else + { + XLogSegNo targetSeg; + uint64 slotKeepSegs; + uint64 keepSegs; + XLogSegNo failSeg; + XLogRecPtr failLSN; + + XLByteToSeg(slot_contents.data.restart_lsn, targetSeg, wal_segment_size); + + /* determine how many segments can be kept by slots */ + slotKeepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size); + /* ditto for wal_keep_size */ + keepSegs = XLogMBVarToSegs(wal_keep_size_mb, wal_segment_size); + + /* if currpos reaches failLSN, we lose our segment */ + failSeg = targetSeg + Max(slotKeepSegs, keepSegs) + 1; + XLogSegNoOffsetToRecPtr(failSeg, 0, wal_segment_size, failLSN); + + values[i++] = Int64GetDatum(failLSN - currlsn); + } + + values[i++] = BoolGetDatum(slot_contents.data.two_phase); + + Assert(i == PG_GET_REPLICATION_SLOTS_COLS); + + tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, + values, nulls); + } + + LWLockRelease(ReplicationSlotControlLock); + + return (Datum) 0; +} + +/* + * Helper function for advancing our physical replication slot forward. + * + * The LSN position to move to is compared simply to the slot's restart_lsn, + * knowing that any position older than that would be removed by successive + * checkpoints. + */ +static XLogRecPtr +pg_physical_replication_slot_advance(XLogRecPtr moveto) +{ + XLogRecPtr startlsn = MyReplicationSlot->data.restart_lsn; + XLogRecPtr retlsn = startlsn; + + Assert(moveto != InvalidXLogRecPtr); + + if (startlsn < moveto) + { + SpinLockAcquire(&MyReplicationSlot->mutex); + MyReplicationSlot->data.restart_lsn = moveto; + SpinLockRelease(&MyReplicationSlot->mutex); + retlsn = moveto; + + /* + * Dirty the slot so as it is written out at the next checkpoint. Note + * that the LSN position advanced may still be lost in the event of a + * crash, but this makes the data consistent after a clean shutdown. + */ + ReplicationSlotMarkDirty(); + } + + return retlsn; +} + +/* + * Helper function for advancing our logical replication slot forward. + * + * The slot's restart_lsn is used as start point for reading records, while + * confirmed_flush is used as base point for the decoding context. + * + * We cannot just do LogicalConfirmReceivedLocation to update confirmed_flush, + * because we need to digest WAL to advance restart_lsn allowing to recycle + * WAL and removal of old catalog tuples. As decoding is done in fast_forward + * mode, no changes are generated anyway. + */ +static XLogRecPtr +pg_logical_replication_slot_advance(XLogRecPtr moveto) +{ + LogicalDecodingContext *ctx; + ResourceOwner old_resowner = CurrentResourceOwner; + XLogRecPtr retlsn; + + Assert(moveto != InvalidXLogRecPtr); + + PG_TRY(); + { + /* + * Create our decoding context in fast_forward mode, passing start_lsn + * as InvalidXLogRecPtr, so that we start processing from my slot's + * confirmed_flush. + */ + ctx = CreateDecodingContext(InvalidXLogRecPtr, + NIL, + true, /* fast_forward */ + XL_ROUTINE(.page_read = read_local_xlog_page, + .segment_open = wal_segment_open, + .segment_close = wal_segment_close), + NULL, NULL, NULL); + + /* + * Start reading at the slot's restart_lsn, which we know to point to + * a valid record. + */ + XLogBeginRead(ctx->reader, MyReplicationSlot->data.restart_lsn); + + /* invalidate non-timetravel entries */ + InvalidateSystemCaches(); + + /* Decode at least one record, until we run out of records */ + while (ctx->reader->EndRecPtr < moveto) + { + char *errm = NULL; + XLogRecord *record; + + /* + * Read records. No changes are generated in fast_forward mode, + * but snapbuilder/slot statuses are updated properly. + */ + record = XLogReadRecord(ctx->reader, &errm); + if (errm) + elog(ERROR, "could not find record while advancing replication slot: %s", + errm); + + /* + * Process the record. Storage-level changes are ignored in + * fast_forward mode, but other modules (such as snapbuilder) + * might still have critical updates to do. + */ + if (record) + LogicalDecodingProcessRecord(ctx, ctx->reader); + + /* Stop once the requested target has been reached */ + if (moveto <= ctx->reader->EndRecPtr) + break; + + CHECK_FOR_INTERRUPTS(); + } + + /* + * Logical decoding could have clobbered CurrentResourceOwner during + * transaction management, so restore the executor's value. (This is + * a kluge, but it's not worth cleaning up right now.) + */ + CurrentResourceOwner = old_resowner; + + if (ctx->reader->EndRecPtr != InvalidXLogRecPtr) + { + LogicalConfirmReceivedLocation(moveto); + + /* + * If only the confirmed_flush LSN has changed the slot won't get + * marked as dirty by the above. Callers on the walsender + * interface are expected to keep track of their own progress and + * don't need it written out. But SQL-interface users cannot + * specify their own start positions and it's harder for them to + * keep track of their progress, so we should make more of an + * effort to save it for them. + * + * Dirty the slot so it is written out at the next checkpoint. The + * LSN position advanced to may still be lost on a crash but this + * makes the data consistent after a clean shutdown. + */ + ReplicationSlotMarkDirty(); + } + + retlsn = MyReplicationSlot->data.confirmed_flush; + + /* free context, call shutdown callback */ + FreeDecodingContext(ctx); + + InvalidateSystemCaches(); + } + PG_CATCH(); + { + /* clear all timetravel entries */ + InvalidateSystemCaches(); + + PG_RE_THROW(); + } + PG_END_TRY(); + + return retlsn; +} + +/* + * SQL function for moving the position in a replication slot. + */ +Datum +pg_replication_slot_advance(PG_FUNCTION_ARGS) +{ + Name slotname = PG_GETARG_NAME(0); + XLogRecPtr moveto = PG_GETARG_LSN(1); + XLogRecPtr endlsn; + XLogRecPtr minlsn; + TupleDesc tupdesc; + Datum values[2]; + bool nulls[2]; + HeapTuple tuple; + Datum result; + + Assert(!MyReplicationSlot); + + CheckSlotPermissions(); + + if (XLogRecPtrIsInvalid(moveto)) + ereport(ERROR, + (errmsg("invalid target WAL LSN"))); + + /* Build a tuple descriptor for our result type */ + if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE) + elog(ERROR, "return type must be a row type"); + + /* + * We can't move slot past what's been flushed/replayed so clamp the + * target position accordingly. + */ + if (!RecoveryInProgress()) + moveto = Min(moveto, GetFlushRecPtr(NULL)); + else + moveto = Min(moveto, GetXLogReplayRecPtr(NULL)); + + /* Acquire the slot so we "own" it */ + ReplicationSlotAcquire(NameStr(*slotname), true); + + /* A slot whose restart_lsn has never been reserved cannot be advanced */ + if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("replication slot \"%s\" cannot be advanced", + NameStr(*slotname)), + errdetail("This slot has never previously reserved WAL, or it has been invalidated."))); + + /* + * Check if the slot is not moving backwards. Physical slots rely simply + * on restart_lsn as a minimum point, while logical slots have confirmed + * consumption up to confirmed_flush, meaning that in both cases data + * older than that is not available anymore. + */ + if (OidIsValid(MyReplicationSlot->data.database)) + minlsn = MyReplicationSlot->data.confirmed_flush; + else + minlsn = MyReplicationSlot->data.restart_lsn; + + if (moveto < minlsn) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot advance replication slot to %X/%X, minimum is %X/%X", + LSN_FORMAT_ARGS(moveto), LSN_FORMAT_ARGS(minlsn)))); + + /* Do the actual slot update, depending on the slot type */ + if (OidIsValid(MyReplicationSlot->data.database)) + endlsn = pg_logical_replication_slot_advance(moveto); + else + endlsn = pg_physical_replication_slot_advance(moveto); + + values[0] = NameGetDatum(&MyReplicationSlot->data.name); + nulls[0] = false; + + /* + * Recompute the minimum LSN and xmin across all slots to adjust with the + * advancing potentially done. + */ + ReplicationSlotsComputeRequiredXmin(false); + ReplicationSlotsComputeRequiredLSN(); + + ReplicationSlotRelease(); + + /* Return the reached position. */ + values[1] = LSNGetDatum(endlsn); + nulls[1] = false; + + tuple = heap_form_tuple(tupdesc, values, nulls); + result = HeapTupleGetDatum(tuple); + + PG_RETURN_DATUM(result); +} + +/* + * Helper function of copying a replication slot. + */ +static Datum +copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot) +{ + Name src_name = PG_GETARG_NAME(0); + Name dst_name = PG_GETARG_NAME(1); + ReplicationSlot *src = NULL; + ReplicationSlot first_slot_contents; + ReplicationSlot second_slot_contents; + XLogRecPtr src_restart_lsn; + bool src_islogical; + bool temporary; + char *plugin; + Datum values[2]; + bool nulls[2]; + Datum result; + TupleDesc tupdesc; + HeapTuple tuple; + + if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE) + elog(ERROR, "return type must be a row type"); + + CheckSlotPermissions(); + + if (logical_slot) + CheckLogicalDecodingRequirements(); + else + CheckSlotRequirements(); + + LWLockAcquire(ReplicationSlotControlLock, LW_SHARED); + + /* + * We need to prevent the source slot's reserved WAL from being removed, + * but we don't want to lock that slot for very long, and it can advance + * in the meantime. So obtain the source slot's data, and create a new + * slot using its restart_lsn. Afterwards we lock the source slot again + * and verify that the data we copied (name, type) has not changed + * incompatibly. No inconvenient WAL removal can occur once the new slot + * is created -- but since WAL removal could have occurred before we + * managed to create the new slot, we advance the new slot's restart_lsn + * to the source slot's updated restart_lsn the second time we lock it. + */ + for (int i = 0; i < max_replication_slots; i++) + { + ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i]; + + if (s->in_use && strcmp(NameStr(s->data.name), NameStr(*src_name)) == 0) + { + /* Copy the slot contents while holding spinlock */ + SpinLockAcquire(&s->mutex); + first_slot_contents = *s; + SpinLockRelease(&s->mutex); + src = s; + break; + } + } + + LWLockRelease(ReplicationSlotControlLock); + + if (src == NULL) + ereport(ERROR, + (errcode(ERRCODE_UNDEFINED_OBJECT), + errmsg("replication slot \"%s\" does not exist", NameStr(*src_name)))); + + src_islogical = SlotIsLogical(&first_slot_contents); + src_restart_lsn = first_slot_contents.data.restart_lsn; + temporary = (first_slot_contents.data.persistency == RS_TEMPORARY); + plugin = logical_slot ? NameStr(first_slot_contents.data.plugin) : NULL; + + /* Check type of replication slot */ + if (src_islogical != logical_slot) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + src_islogical ? + errmsg("cannot copy physical replication slot \"%s\" as a logical replication slot", + NameStr(*src_name)) : + errmsg("cannot copy logical replication slot \"%s\" as a physical replication slot", + NameStr(*src_name)))); + + /* Copying non-reserved slot doesn't make sense */ + if (XLogRecPtrIsInvalid(src_restart_lsn)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot copy a replication slot that doesn't reserve WAL"))); + + /* Overwrite params from optional arguments */ + if (PG_NARGS() >= 3) + temporary = PG_GETARG_BOOL(2); + if (PG_NARGS() >= 4) + { + Assert(logical_slot); + plugin = NameStr(*(PG_GETARG_NAME(3))); + } + + /* Create new slot and acquire it */ + if (logical_slot) + { + /* + * We must not try to read WAL, since we haven't reserved it yet -- + * hence pass find_startpoint false. confirmed_flush will be set + * below, by copying from the source slot. + */ + create_logical_replication_slot(NameStr(*dst_name), + plugin, + temporary, + false, + src_restart_lsn, + false); + } + else + create_physical_replication_slot(NameStr(*dst_name), + true, + temporary, + src_restart_lsn); + + /* + * Update the destination slot to current values of the source slot; + * recheck that the source slot is still the one we saw previously. + */ + { + TransactionId copy_effective_xmin; + TransactionId copy_effective_catalog_xmin; + TransactionId copy_xmin; + TransactionId copy_catalog_xmin; + XLogRecPtr copy_restart_lsn; + XLogRecPtr copy_confirmed_flush; + bool copy_islogical; + char *copy_name; + + /* Copy data of source slot again */ + SpinLockAcquire(&src->mutex); + second_slot_contents = *src; + SpinLockRelease(&src->mutex); + + copy_effective_xmin = second_slot_contents.effective_xmin; + copy_effective_catalog_xmin = second_slot_contents.effective_catalog_xmin; + + copy_xmin = second_slot_contents.data.xmin; + copy_catalog_xmin = second_slot_contents.data.catalog_xmin; + copy_restart_lsn = second_slot_contents.data.restart_lsn; + copy_confirmed_flush = second_slot_contents.data.confirmed_flush; + + /* for existence check */ + copy_name = NameStr(second_slot_contents.data.name); + copy_islogical = SlotIsLogical(&second_slot_contents); + + /* + * Check if the source slot still exists and is valid. We regard it as + * invalid if the type of replication slot or name has been changed, + * or the restart_lsn either is invalid or has gone backward. (The + * restart_lsn could go backwards if the source slot is dropped and + * copied from an older slot during installation.) + * + * Since erroring out will release and drop the destination slot we + * don't need to release it here. + */ + if (copy_restart_lsn < src_restart_lsn || + src_islogical != copy_islogical || + strcmp(copy_name, NameStr(*src_name)) != 0) + ereport(ERROR, + (errmsg("could not copy replication slot \"%s\"", + NameStr(*src_name)), + errdetail("The source replication slot was modified incompatibly during the copy operation."))); + + /* The source slot must have a consistent snapshot */ + if (src_islogical && XLogRecPtrIsInvalid(copy_confirmed_flush)) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("cannot copy unfinished logical replication slot \"%s\"", + NameStr(*src_name)), + errhint("Retry when the source replication slot's confirmed_flush_lsn is valid."))); + + /* Install copied values again */ + SpinLockAcquire(&MyReplicationSlot->mutex); + MyReplicationSlot->effective_xmin = copy_effective_xmin; + MyReplicationSlot->effective_catalog_xmin = copy_effective_catalog_xmin; + + MyReplicationSlot->data.xmin = copy_xmin; + MyReplicationSlot->data.catalog_xmin = copy_catalog_xmin; + MyReplicationSlot->data.restart_lsn = copy_restart_lsn; + MyReplicationSlot->data.confirmed_flush = copy_confirmed_flush; + SpinLockRelease(&MyReplicationSlot->mutex); + + ReplicationSlotMarkDirty(); + ReplicationSlotsComputeRequiredXmin(false); + ReplicationSlotsComputeRequiredLSN(); + ReplicationSlotSave(); + +#ifdef USE_ASSERT_CHECKING + /* Check that the restart_lsn is available */ + { + XLogSegNo segno; + + XLByteToSeg(copy_restart_lsn, segno, wal_segment_size); + Assert(XLogGetLastRemovedSegno() < segno); + } +#endif + } + + /* target slot fully created, mark as persistent if needed */ + if (logical_slot && !temporary) + ReplicationSlotPersist(); + + /* All done. Set up the return values */ + values[0] = NameGetDatum(dst_name); + nulls[0] = false; + if (!XLogRecPtrIsInvalid(MyReplicationSlot->data.confirmed_flush)) + { + values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush); + nulls[1] = false; + } + else + nulls[1] = true; + + tuple = heap_form_tuple(tupdesc, values, nulls); + result = HeapTupleGetDatum(tuple); + + ReplicationSlotRelease(); + + PG_RETURN_DATUM(result); +} + +/* The wrappers below are all to appease opr_sanity */ +Datum +pg_copy_logical_replication_slot_a(PG_FUNCTION_ARGS) +{ + return copy_replication_slot(fcinfo, true); +} + +Datum +pg_copy_logical_replication_slot_b(PG_FUNCTION_ARGS) +{ + return copy_replication_slot(fcinfo, true); +} + +Datum +pg_copy_logical_replication_slot_c(PG_FUNCTION_ARGS) +{ + return copy_replication_slot(fcinfo, true); +} + +Datum +pg_copy_physical_replication_slot_a(PG_FUNCTION_ARGS) +{ + return copy_replication_slot(fcinfo, false); +} + +Datum +pg_copy_physical_replication_slot_b(PG_FUNCTION_ARGS) +{ + return copy_replication_slot(fcinfo, false); +} |