/* * Report the current WAL flush location (same format as pg_start_backup etc) * * This function is mostly for debugging purposes. */ Datum pg_current_xlog_flush_location(PG_FUNCTION_ARGS) { XLogRecPtr current_recptr; if (RecoveryInProgress()) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("recovery is in progress"), errhint("WAL control functions cannot be executed during recovery."))); current_recptr = GetFlushRecPtr(); PG_RETURN_LSN(current_recptr); }
/* * read_page callback for logical decoding contexts. * * Public because it would likely be very helpful for someone writing another * output method outside walsender, e.g. in a bgworker. * * TODO: The walsender has it's own version of this, but it relies on the * walsender's latch being set whenever WAL is flushed. No such infrastructure * exists for normal backends, so we have to do a check/sleep/repeat style of * loop for now. */ int logical_read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetRecPtr, char *cur_page, TimeLineID *pageTLI) { XLogRecPtr flushptr, loc; int count; loc = targetPagePtr + reqLen; while (1) { /* * TODO: we're going to have to do something more intelligent about * timelines on standbys. Use readTimeLineHistory() and * tliOfPointInHistory() to get the proper LSN? For now we'll catch * that case earlier, but the code and TODO is left in here for when * that changes. */ if (!RecoveryInProgress()) { *pageTLI = ThisTimeLineID; flushptr = GetFlushRecPtr(); } else flushptr = GetXLogReplayRecPtr(pageTLI); if (loc <= flushptr) break; CHECK_FOR_INTERRUPTS(); pg_usleep(1000L); } /* more than one block available */ if (targetPagePtr + XLOG_BLCKSZ <= flushptr) count = XLOG_BLCKSZ; /* not enough data there */ else if (targetPagePtr + reqLen > flushptr) return -1; /* part of the page available */ else count = flushptr - targetPagePtr; XLogRead(cur_page, *pageTLI, targetPagePtr, XLOG_BLCKSZ); return count; }
/* * Read up to MAX_SEND_SIZE bytes of WAL that's been flushed to disk, * but not yet sent to the client, and buffer it in the libpq output * buffer. * * msgbuf is a work area in which the output message is constructed. It's * passed in just so we can avoid re-palloc'ing the buffer on each cycle. * It must be of size 1 + sizeof(WalDataMessageHeader) + MAX_SEND_SIZE. * * If there is no unsent WAL remaining, *caughtup is set to true, otherwise * *caughtup is set to false. */ static void XLogSend(char *msgbuf, bool *caughtup) { XLogRecPtr SendRqstPtr; XLogRecPtr startptr; XLogRecPtr endptr; Size nbytes; WalDataMessageHeader msghdr; /* * Attempt to send all data that's already been written out and fsync'd to * disk. We cannot go further than what's been written out given the * current implementation of XLogRead(). And in any case it's unsafe to * send WAL that is not securely down to disk on the master: if the master * subsequently crashes and restarts, slaves must not have applied any WAL * that gets lost on the master. */ SendRqstPtr = am_cascading_walsender ? GetStandbyFlushRecPtr() : GetFlushRecPtr(); /* Quick exit if nothing to do */ if (XLByteLE(SendRqstPtr, sentPtr)) { *caughtup = true; return; } /* * Figure out how much to send in one message. If there's no more than * MAX_SEND_SIZE bytes to send, send everything. Otherwise send * MAX_SEND_SIZE bytes, but round back to logfile or page boundary. * * The rounding is not only for performance reasons. Walreceiver relies on * the fact that we never split a WAL record across two messages. Since a * long WAL record is split at page boundary into continuation records, * page boundary is always a safe cut-off point. We also assume that * SendRqstPtr never points to the middle of a WAL record. */ startptr = sentPtr; if (startptr.xrecoff >= XLogFileSize) { /* * crossing a logid boundary, skip the non-existent last log segment * in previous logical log file. */ startptr.xlogid += 1; startptr.xrecoff = 0; } endptr = startptr; XLByteAdvance(endptr, MAX_SEND_SIZE); if (endptr.xlogid != startptr.xlogid) { /* Don't cross a logfile boundary within one message */ Assert(endptr.xlogid == startptr.xlogid + 1); endptr.xlogid = startptr.xlogid; endptr.xrecoff = XLogFileSize; } /* if we went beyond SendRqstPtr, back off */ if (XLByteLE(SendRqstPtr, endptr)) { endptr = SendRqstPtr; *caughtup = true; } else { /* round down to page boundary. */ endptr.xrecoff -= (endptr.xrecoff % XLOG_BLCKSZ); *caughtup = false; } nbytes = endptr.xrecoff - startptr.xrecoff; Assert(nbytes <= MAX_SEND_SIZE); /* * OK to read and send the slice. */ msgbuf[0] = 'w'; /* * Read the log directly into the output buffer to avoid extra memcpy * calls. */ XLogRead(msgbuf + 1 + sizeof(WalDataMessageHeader), startptr, nbytes); /* * We fill the message header last so that the send timestamp is taken as * late as possible. */ msghdr.dataStart = startptr; msghdr.walEnd = SendRqstPtr; msghdr.sendTime = GetCurrentTimestamp(); memcpy(msgbuf + 1, &msghdr, sizeof(WalDataMessageHeader)); pq_putmessage_noblock('d', msgbuf, 1 + sizeof(WalDataMessageHeader) + nbytes); sentPtr = endptr; /* Update shared memory status */ { /* use volatile pointer to prevent code rearrangement */ volatile WalSnd *walsnd = MyWalSnd; SpinLockAcquire(&walsnd->mutex); walsnd->sentPtr = sentPtr; SpinLockRelease(&walsnd->mutex); } /* Report progress of XLOG streaming in PS display */ if (update_process_title) { char activitymsg[50]; snprintf(activitymsg, sizeof(activitymsg), "streaming %X/%X", sentPtr.xlogid, sentPtr.xrecoff); set_ps_display(activitymsg, false); } return; }
/* * Helper function for the various SQL callable logical decoding functions. */ static Datum pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool binary) { Name name; XLogRecPtr upto_lsn; int32 upto_nchanges; ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo; MemoryContext per_query_ctx; MemoryContext oldcontext; XLogRecPtr end_of_wal; XLogRecPtr startptr; LogicalDecodingContext *ctx; ResourceOwner old_resowner = CurrentResourceOwner; ArrayType *arr; Size ndim; List *options = NIL; DecodingOutputState *p; check_permissions(); CheckLogicalDecodingRequirements(); if (PG_ARGISNULL(0)) ereport(ERROR, (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED), errmsg("slot name must not be null"))); name = PG_GETARG_NAME(0); if (PG_ARGISNULL(1)) upto_lsn = InvalidXLogRecPtr; else upto_lsn = PG_GETARG_LSN(1); if (PG_ARGISNULL(2)) upto_nchanges = InvalidXLogRecPtr; else upto_nchanges = PG_GETARG_INT32(2); if (PG_ARGISNULL(3)) ereport(ERROR, (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED), errmsg("options array must not be null"))); arr = PG_GETARG_ARRAYTYPE_P(3); /* check to see if caller supports us returning a tuplestore */ if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("set-valued function called in context that cannot accept a set"))); if (!(rsinfo->allowedModes & SFRM_Materialize)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("materialize mode required, but it is not allowed in this context"))); /* state to write output to */ p = palloc0(sizeof(DecodingOutputState)); p->binary_output = binary; /* Build a tuple descriptor for our result type */ if (get_call_result_type(fcinfo, NULL, &p->tupdesc) != TYPEFUNC_COMPOSITE) elog(ERROR, "return type must be a row type"); per_query_ctx = rsinfo->econtext->ecxt_per_query_memory; oldcontext = MemoryContextSwitchTo(per_query_ctx); /* Deconstruct options array */ ndim = ARR_NDIM(arr); if (ndim > 1) { ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("array must be one-dimensional"))); } else if (array_contains_nulls(arr)) { ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("array must not contain nulls"))); } else if (ndim == 1) { int nelems; Datum *datum_opts; int i; Assert(ARR_ELEMTYPE(arr) == TEXTOID); deconstruct_array(arr, TEXTOID, -1, false, 'i', &datum_opts, NULL, &nelems); if (nelems % 2 != 0) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("array must have even number of elements"))); for (i = 0; i < nelems; i += 2) { char *name = TextDatumGetCString(datum_opts[i]); char *opt = TextDatumGetCString(datum_opts[i + 1]); options = lappend(options, makeDefElem(name, (Node *) makeString(opt), -1)); } } p->tupstore = tuplestore_begin_heap(true, false, work_mem); rsinfo->returnMode = SFRM_Materialize; rsinfo->setResult = p->tupstore; rsinfo->setDesc = p->tupdesc; /* * Compute the current end-of-wal and maintain ThisTimeLineID. * RecoveryInProgress() will update ThisTimeLineID on promotion. */ if (!RecoveryInProgress()) end_of_wal = GetFlushRecPtr(); else end_of_wal = GetXLogReplayRecPtr(&ThisTimeLineID); ReplicationSlotAcquire(NameStr(*name), true); PG_TRY(); { /* restart at slot's confirmed_flush */ ctx = CreateDecodingContext(InvalidXLogRecPtr, options, false, logical_read_local_xlog_page, LogicalOutputPrepareWrite, LogicalOutputWrite, NULL); MemoryContextSwitchTo(oldcontext); /* * Check whether the output plugin writes textual output if that's * what we need. */ if (!binary && ctx->options.output_type !=OUTPUT_PLUGIN_TEXTUAL_OUTPUT) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("logical decoding output plugin \"%s\" produces binary output, but function \"%s\" expects textual data", NameStr(MyReplicationSlot->data.plugin), format_procedure(fcinfo->flinfo->fn_oid)))); ctx->output_writer_private = p; /* * Decoding of WAL must start at restart_lsn so that the entirety of * xacts that committed after the slot's confirmed_flush can be * accumulated into reorder buffers. */ startptr = MyReplicationSlot->data.restart_lsn; CurrentResourceOwner = ResourceOwnerCreate(CurrentResourceOwner, "logical decoding"); /* invalidate non-timetravel entries */ InvalidateSystemCaches(); /* Decode until we run out of records */ while ((startptr != InvalidXLogRecPtr && startptr < end_of_wal) || (ctx->reader->EndRecPtr != InvalidXLogRecPtr && ctx->reader->EndRecPtr < end_of_wal)) { XLogRecord *record; char *errm = NULL; record = XLogReadRecord(ctx->reader, startptr, &errm); if (errm) elog(ERROR, "%s", errm); /* * Now that we've set up the xlog reader state, subsequent calls * pass InvalidXLogRecPtr to say "continue from last record" */ startptr = InvalidXLogRecPtr; /* * The {begin_txn,change,commit_txn}_wrapper callbacks above will * store the description into our tuplestore. */ if (record != NULL) LogicalDecodingProcessRecord(ctx, ctx->reader); /* check limits */ if (upto_lsn != InvalidXLogRecPtr && upto_lsn <= ctx->reader->EndRecPtr) break; if (upto_nchanges != 0 && upto_nchanges <= p->returned_rows) break; CHECK_FOR_INTERRUPTS(); } tuplestore_donestoring(tupstore); CurrentResourceOwner = old_resowner; /* * Next time, start where we left off. (Hunting things, the family * business..) */ if (ctx->reader->EndRecPtr != InvalidXLogRecPtr && confirm) { LogicalConfirmReceivedLocation(ctx->reader->EndRecPtr); /* * 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's written out at the next checkpoint. * We'll still lose its position on crash, as documented, but it's * better than always losing the position even on clean restart. */ ReplicationSlotMarkDirty(); } /* free context, call shutdown callback */ FreeDecodingContext(ctx); ReplicationSlotRelease(); InvalidateSystemCaches(); } PG_CATCH(); { /* clear all timetravel entries */ InvalidateSystemCaches(); PG_RE_THROW(); } PG_END_TRY(); return (Datum) 0; }
/* * Helper function for the various SQL callable logical decoding functions. */ static Datum pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool binary) { Name name = PG_GETARG_NAME(0); XLogRecPtr upto_lsn; int32 upto_nchanges; ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo; MemoryContext per_query_ctx; MemoryContext oldcontext; XLogRecPtr end_of_wal; XLogRecPtr startptr; LogicalDecodingContext *ctx; ResourceOwner old_resowner = CurrentResourceOwner; ArrayType *arr; Size ndim; List *options = NIL; DecodingOutputState *p; if (PG_ARGISNULL(1)) upto_lsn = InvalidXLogRecPtr; else upto_lsn = PG_GETARG_LSN(1); if (PG_ARGISNULL(2)) upto_nchanges = InvalidXLogRecPtr; else upto_nchanges = PG_GETARG_INT32(2); /* check to see if caller supports us returning a tuplestore */ if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("set-valued function called in context that cannot accept a set"))); if (!(rsinfo->allowedModes & SFRM_Materialize)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("materialize mode required, but it is not allowed in this context"))); /* state to write output to */ p = palloc0(sizeof(DecodingOutputState)); p->binary_output = binary; /* Build a tuple descriptor for our result type */ if (get_call_result_type(fcinfo, NULL, &p->tupdesc) != TYPEFUNC_COMPOSITE) elog(ERROR, "return type must be a row type"); check_permissions(); CheckLogicalDecodingRequirements(); arr = PG_GETARG_ARRAYTYPE_P(3); ndim = ARR_NDIM(arr); per_query_ctx = rsinfo->econtext->ecxt_per_query_memory; oldcontext = MemoryContextSwitchTo(per_query_ctx); if (ndim > 1) { ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("array must be one-dimensional"))); } else if (array_contains_nulls(arr)) { ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("array must not contain nulls"))); } else if (ndim == 1) { int nelems; Datum *datum_opts; int i; Assert(ARR_ELEMTYPE(arr) == TEXTOID); deconstruct_array(arr, TEXTOID, -1, false, 'i', &datum_opts, NULL, &nelems); if (nelems % 2 != 0) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("array must have even number of elements"))); for (i = 0; i < nelems; i += 2) { char *name = TextDatumGetCString(datum_opts[i]); char *opt = TextDatumGetCString(datum_opts[i + 1]); options = lappend(options, makeDefElem(name, (Node *) makeString(opt))); } } p->tupstore = tuplestore_begin_heap(true, false, work_mem); rsinfo->returnMode = SFRM_Materialize; rsinfo->setResult = p->tupstore; rsinfo->setDesc = p->tupdesc; /* compute the current end-of-wal */ if (!RecoveryInProgress()) end_of_wal = GetFlushRecPtr(); else end_of_wal = GetXLogReplayRecPtr(NULL); CheckLogicalDecodingRequirements(); ReplicationSlotAcquire(NameStr(*name)); PG_TRY(); { ctx = CreateDecodingContext(InvalidXLogRecPtr, options, logical_read_local_xlog_page, LogicalOutputPrepareWrite, LogicalOutputWrite); MemoryContextSwitchTo(oldcontext); /* * Check whether the output pluggin writes textual output if that's * what we need. */ if (!binary && ctx->options.output_type != OUTPUT_PLUGIN_TEXTUAL_OUTPUT) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("output plugin cannot produce binary output"))); ctx->output_writer_private = p; startptr = MyReplicationSlot->data.restart_lsn; CurrentResourceOwner = ResourceOwnerCreate(CurrentResourceOwner, "logical decoding"); /* invalidate non-timetravel entries */ InvalidateSystemCaches(); while ((startptr != InvalidXLogRecPtr && startptr < end_of_wal) || (ctx->reader->EndRecPtr && ctx->reader->EndRecPtr < end_of_wal)) { XLogRecord *record; char *errm = NULL; record = XLogReadRecord(ctx->reader, startptr, &errm); if (errm) elog(ERROR, "%s", errm); startptr = InvalidXLogRecPtr; /* * The {begin_txn,change,commit_txn}_wrapper callbacks above will * store the description into our tuplestore. */ if (record != NULL) LogicalDecodingProcessRecord(ctx, record); /* check limits */ if (upto_lsn != InvalidXLogRecPtr && upto_lsn <= ctx->reader->EndRecPtr) break; if (upto_nchanges != 0 && upto_nchanges <= p->returned_rows) break; } } PG_CATCH(); { /* clear all timetravel entries */ InvalidateSystemCaches(); PG_RE_THROW(); } PG_END_TRY(); tuplestore_donestoring(tupstore); CurrentResourceOwner = old_resowner; /* * Next time, start where we left off. (Hunting things, the family * business..) */ if (ctx->reader->EndRecPtr != InvalidXLogRecPtr && confirm) LogicalConfirmReceivedLocation(ctx->reader->EndRecPtr); /* free context, call shutdown callback */ FreeDecodingContext(ctx); ReplicationSlotRelease(); InvalidateSystemCaches(); return (Datum) 0; }