From: Andrey V. Lepikhov <a.lepikhov@postgrespro.ru>
To: PostgreSQL-Dev <pgsql-hackers@postgresql.org>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Subject: Re: Global snapshots
Date: Fri, 19 Nov 2021 16:10:59 +0500
Message-ID: <2983d675-7076-083a-aac7-b35d84c7d6ff@postgrespro.ru> (raw)
In-Reply-To: <TYAPR01MB299037242B6A5C0B6F9C84AEFE629@TYAPR01MB2990.jpnprd01.prod.outlook.com>
References: <07b2c899-4ed0-4c87-1327-23c750311248@postgrespro.ru>
<d17da3c0-54bb-6221-7ec7-151f6be39e5f@oss.nttdata.com>
<TYAPR01MB299093D3F5E8BC2D80D5DFD6FE270@TYAPR01MB2990.jpnprd01.prod.outlook.com>
<88a2642f-1ce6-a9d2-5d26-1221a2c4e072@oss.nttdata.com>
<CAA4eK1LMQYtY1kJX5RpxkUCnrFnGqj--zcAGVH7Sp3mcPRRuvg@mail.gmail.com>
<dc6d5fe2-7bdf-1b3f-1027-e152b979c12f@oss.nttdata.com>
<CA+fd4k5d9Jjt2zwCFwm9FmFF1m6J1_ixaU_X7noM9qkDWCbAzA@mail.gmail.com>
<f59e3cf8-84d7-4a2b-218d-48ffac488566@oss.nttdata.com>
<TYAPR01MB299083299DA94BA849358BEEFE170@TYAPR01MB2990.jpnprd01.prod.outlook.com>
<TYAPR01MB2990CAC9CE3D0AA63B45053CFED50@TYAPR01MB2990.jpnprd01.prod.outlook.com>
<a0503174-9ac9-fe2c-1788-1a1337d72453@postgrespro.ru>
<TYAPR01MB299079A57E722E71869DBE0CFE9D9@TYAPR01MB2990.jpnprd01.prod.outlook.com>
<0e65f96f-bfd6-fb09-89b7-e07854c215e6@postgrespro.ru>
<TYAPR01MB299037242B6A5C0B6F9C84AEFE629@TYAPR01MB2990.jpnprd01.prod.outlook.com>
Patch in the previous letter is full of faulties. Please, use new version.
Also, here we fixed the problem with loosing CSN value in a parallel
worker (TAP test 003_parallel_safe.pl). Thanks for a.pyhalov for the
problem detection and a bugfix.
--
regards,
Andrey Lepikhov
Postgres Professional
Attachments:
[text/x-patch] v2-0001-Add-Commit-Sequence-Number-CSN-machinery-into-MVCC.patch (118.5K, ../2983d675-7076-083a-aac7-b35d84c7d6ff@postgrespro.ru/2-v2-0001-Add-Commit-Sequence-Number-CSN-machinery-into-MVCC.patch)
download | inline diff:
From 7aa57724fc42b8ca7054f9b6edfa33c0cffb24bf Mon Sep 17 00:00:00 2001
From: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
Date: Wed, 17 Nov 2021 11:13:37 +0500
Subject: [PATCH] Add Commit Sequence Number (CSN) machinery into MVCC
implementation for a timestamp-based resolving of visibility conflicts.
It allows to achieve proper snapshot isolation semantics in the case
of distributed transactions involving more than one Postgres instance.
Authors: K.Knizhnik, S.Kelvich, A.Sher, A.Lepikhov, M.Usama.
Discussion:
(2020/05/21 -)
https://www.postgresql.org/message-id/flat/CA%2Bfd4k6HE8xLGEvqWzABEg8kkju5MxU%2Bif7bf-md0_2pjzXp9Q%40mail.gmail.com#ed1359340871688bed2e643921f73365
(2018/05/01 - 2019/04/21)
https://www.postgresql.org/message-id/flat/21BC916B-80A1-43BF-8650-3363CCDAE09C%40postgrespro.ru
---
doc/src/sgml/config.sgml | 50 +-
src/backend/access/rmgrdesc/Makefile | 1 +
src/backend/access/rmgrdesc/csnlogdesc.c | 95 +++
src/backend/access/rmgrdesc/xlogdesc.c | 6 +-
src/backend/access/transam/Makefile | 2 +
src/backend/access/transam/csn_log.c | 748 ++++++++++++++++++
src/backend/access/transam/csn_snapshot.c | 687 ++++++++++++++++
src/backend/access/transam/rmgr.c | 1 +
src/backend/access/transam/twophase.c | 154 ++++
src/backend/access/transam/varsup.c | 2 +
src/backend/access/transam/xact.c | 32 +
src/backend/access/transam/xlog.c | 23 +-
src/backend/access/transam/xloginsert.c | 2 +
src/backend/commands/vacuum.c | 3 +-
src/backend/replication/logical/snapbuild.c | 4 +
src/backend/storage/ipc/ipci.c | 6 +
src/backend/storage/ipc/procarray.c | 85 ++
src/backend/storage/lmgr/lwlock.c | 2 +
src/backend/storage/lmgr/lwlocknames.txt | 2 +
src/backend/storage/lmgr/proc.c | 6 +
src/backend/storage/sync/sync.c | 5 +
src/backend/utils/misc/guc.c | 37 +
src/backend/utils/probes.d | 2 +
src/backend/utils/time/snapmgr.c | 183 ++++-
src/bin/initdb/initdb.c | 3 +-
src/bin/pg_controldata/pg_controldata.c | 2 +
src/bin/pg_upgrade/pg_upgrade.c | 5 +
src/bin/pg_upgrade/pg_upgrade.h | 2 +
src/bin/pg_waldump/rmgrdesc.c | 1 +
src/include/access/csn_log.h | 98 +++
src/include/access/csn_snapshot.h | 54 ++
src/include/access/rmgrlist.h | 1 +
src/include/access/xlog_internal.h | 2 +
src/include/catalog/pg_control.h | 1 +
src/include/catalog/pg_proc.dat | 17 +
src/include/datatype/timestamp.h | 3 +
src/include/fmgr.h | 1 +
src/include/portability/instr_time.h | 10 +
src/include/storage/lwlock.h | 1 +
src/include/storage/proc.h | 14 +
src/include/storage/procarray.h | 7 +
src/include/storage/sync.h | 1 +
src/include/utils/snapmgr.h | 7 +-
src/include/utils/snapshot.h | 11 +
src/test/modules/Makefile | 1 +
src/test/modules/csnsnapshot/Makefile | 22 +
.../csnsnapshot/expected/csnsnapshot.out | 1 +
src/test/modules/csnsnapshot/t/001_base.pl | 100 +++
src/test/modules/csnsnapshot/t/002_standby.pl | 68 ++
.../csnsnapshot/t/003_parallel_safe.pl | 67 ++
src/test/modules/snapshot_too_old/sto.conf | 1 +
src/test/perl/PostgreSQL/Test/Cluster.pm | 28 +
src/test/regress/expected/sysviews.out | 4 +-
53 files changed, 2660 insertions(+), 11 deletions(-)
create mode 100644 src/backend/access/rmgrdesc/csnlogdesc.c
create mode 100644 src/backend/access/transam/csn_log.c
create mode 100644 src/backend/access/transam/csn_snapshot.c
create mode 100644 src/include/access/csn_log.h
create mode 100644 src/include/access/csn_snapshot.h
create mode 100644 src/test/modules/csnsnapshot/Makefile
create mode 100644 src/test/modules/csnsnapshot/expected/csnsnapshot.out
create mode 100644 src/test/modules/csnsnapshot/t/001_base.pl
create mode 100644 src/test/modules/csnsnapshot/t/002_standby.pl
create mode 100644 src/test/modules/csnsnapshot/t/003_parallel_safe.pl
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgmlindex 3f806740d5..f4f6c83fd0 100644--- a/doc/src/sgml/config.sgml+++ b/doc/src/sgml/config.sgml@@ -9682,8 +9682,56 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
</varlistentry>
</variablelist>
- </sect1>+ <sect2 id="runtime-config-CSN-based-snapshot">+ <title>CSN Based Snapshot</title>+ <para>+ By default, snapshots in <productname>PostgreSQL</productname> contains a+ XID (TransactionID) that allows to identify the status of a transaction+ and make arbitrary visibility calculations.+ </para>++ <para>+ <productname>PostgreSQL</productname> also provides a CSN (Commit+ Sequence Number) based machinery as an additional tool for visibility+ calculations. It may be used within distributed transactions when a xid of+ a local transaction can't correctly identify order of the distributed one.+ </para>++ <variablelist>+ <varlistentry id="guc-enable-csn-snapshot" xreflabel="enable_csn_snapshot">+ <term><varname>enable_csn_snapshot</varname> (<type>boolean</type>)+ <indexterm>+ <primary><varname>enable_csn_snapshot</varname> configuration parameter</primary>+ </indexterm>+ </term>+ <listitem>++ <para>+ Enable/disable the CSN tracking for the snapshot.+ </para>++ <para>+ <productname>PostgreSQL</productname> uses a physical clock timestamp as+ a CSN, so enabling the CSN based snapshots can be useful for implementing+ cross-instance snapshots and visibility of distributed transaction.+ </para>++ <para>+ when enabled <productname>PostgreSQL</productname> creates+ <filename>pg_csn</filename> directory under <envar>PGDATA</envar> to keep+ the track of CSN and XID mappings.+ </para>++ <para>+ The default value is on.+ </para>+ </listitem>+ </varlistentry>++ </variablelist>+ </sect2>+ </sect1>
<sect1 id="runtime-config-compatible">
<title>Version and Platform Compatibility</title>
diff --git a/src/backend/access/rmgrdesc/Makefile b/src/backend/access/rmgrdesc/Makefileindex f88d72fd86..15fc36f7b4 100644--- a/src/backend/access/rmgrdesc/Makefile+++ b/src/backend/access/rmgrdesc/Makefile@@ -11,6 +11,7 @@ include $(top_builddir)/src/Makefile.global
OBJS = \
brindesc.o \
clogdesc.o \
+ csnlogdesc.o \
committsdesc.o \
dbasedesc.o \
genericdesc.o \
diff --git a/src/backend/access/rmgrdesc/csnlogdesc.c b/src/backend/access/rmgrdesc/csnlogdesc.cnew file mode 100644index 0000000000..f8c644e906--- /dev/null+++ b/src/backend/access/rmgrdesc/csnlogdesc.c@@ -0,0 +1,95 @@+/*-------------------------------------------------------------------------+ *+ * clogdesc.c+ * rmgr descriptor routines for access/transam/csn_log.c+ *+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group+ * Portions Copyright (c) 1994, Regents of the University of California+ *+ *+ * IDENTIFICATION+ * src/backend/access/rmgrdesc/csnlogdesc.c+ *+ *-------------------------------------------------------------------------+ */+#include "postgres.h"++#include "access/csn_log.h"+++void+csnlog_desc(StringInfo buf, XLogReaderState *record)+{+ char *rec = XLogRecGetData(record);+ uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;++ if (info == XLOG_CSN_ZEROPAGE)+ {+ int pageno;++ memcpy(&pageno, XLogRecGetData(record), sizeof(int));+ appendStringInfo(buf, "pageno %d", pageno);+ }+ else if (info == XLOG_CSN_TRUNCATE)+ {+ int pageno;++ memcpy(&pageno, XLogRecGetData(record), sizeof(int));+ appendStringInfo(buf, "pageno %d", pageno);+ }+ else if (info == XLOG_CSN_ASSIGNMENT)+ {+ CSN csn;++ memcpy(&csn, XLogRecGetData(record), sizeof(CSN));+ appendStringInfo(buf, "assign "INT64_FORMAT"", csn);+ }+ else if (info == XLOG_CSN_SETCSN)+ {+ xl_csn_set *xlrec = (xl_csn_set *) rec;+ int nsubxids;++ appendStringInfo(buf, "set "INT64_FORMAT" for: %u",+ xlrec->csn,+ xlrec->xtop);+ nsubxids = ((XLogRecGetDataLen(record) - MinSizeOfCSNSet) /+ sizeof(TransactionId));+ if (nsubxids > 0)+ {+ int i;+ TransactionId *subxids;++ subxids = palloc(sizeof(TransactionId) * nsubxids);+ memcpy(subxids,+ XLogRecGetData(record) + MinSizeOfCSNSet,+ sizeof(TransactionId) * nsubxids);+ for (i = 0; i < nsubxids; i++)+ appendStringInfo(buf, ", %u", subxids[i]);+ pfree(subxids);+ }+ }+}++const char *+csnlog_identify(uint8 info)+{+ const char *id = NULL;++ switch (info & ~XLR_INFO_MASK)+ {+ case XLOG_CSN_ASSIGNMENT:+ id = "ASSIGNMENT";+ break;+ case XLOG_CSN_SETCSN:+ id = "SETCSN";+ break;+ case XLOG_CSN_ZEROPAGE:+ id = "ZEROPAGE";+ break;+ case XLOG_CSN_TRUNCATE:+ id = "TRUNCATE";+ break;+ }++ return id;+}diff --git a/src/backend/access/rmgrdesc/xlogdesc.c b/src/backend/access/rmgrdesc/xlogdesc.cindex 5bf2346dd9..ea433046cf 100644--- a/src/backend/access/rmgrdesc/xlogdesc.c+++ b/src/backend/access/rmgrdesc/xlogdesc.c@@ -113,7 +113,8 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
appendStringInfo(buf, "max_connections=%d max_worker_processes=%d "
"max_wal_senders=%d max_prepared_xacts=%d "
"max_locks_per_xact=%d wal_level=%s "
- "wal_log_hints=%s track_commit_timestamp=%s",+ "wal_log_hints=%s track_commit_timestamp=%s "+ "enable_csn_snapshot=%s",
xlrec.MaxConnections,
xlrec.max_worker_processes,
xlrec.max_wal_senders,
@@ -121,7 +122,8 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
xlrec.max_locks_per_xact,
wal_level_str,
xlrec.wal_log_hints ? "on" : "off",
- xlrec.track_commit_timestamp ? "on" : "off");+ xlrec.track_commit_timestamp ? "on" : "off",+ xlrec.enable_csn_snapshot ? "on" : "off");
}
else if (info == XLOG_FPW_CHANGE)
{
diff --git a/src/backend/access/transam/Makefile b/src/backend/access/transam/Makefileindex 595e02de72..fc0321ee6b 100644--- a/src/backend/access/transam/Makefile+++ b/src/backend/access/transam/Makefile@@ -15,6 +15,8 @@ include $(top_builddir)/src/Makefile.global
OBJS = \
clog.o \
commit_ts.o \
+ csn_log.o \+ csn_snapshot.o \
generic_xlog.o \
multixact.o \
parallel.o \
diff --git a/src/backend/access/transam/csn_log.c b/src/backend/access/transam/csn_log.cnew file mode 100644index 0000000000..33517271ed--- /dev/null+++ b/src/backend/access/transam/csn_log.c@@ -0,0 +1,748 @@+/*-----------------------------------------------------------------------------+ *+ * csn_log.c+ * Track commit sequence numbers of finished transactions+ *+ * This module provides SLRU to store CSN for each transaction. This+ * mapping need to be kept only for xid's greater then oldestXid, but+ * that can require arbitrary large amounts of memory in case of long-lived+ * transactions. Because of same lifetime and persistancy requirements+ * this module is quite similar to subtrans.c+ *+ * If we switch database from CSN-base snapshot to xid-base snapshot then,+ * nothing wrong. But if we switch xid-base snapshot to CSN-base snapshot+ * it should decide a new xid which begin csn-base check. It can not be+ * oldestActiveXID because of prepared transaction.+ *+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group+ * Portions Copyright (c) 1994, Regents of the University of California+ *+ * src/backend/access/transam/csn_log.c+ *+ *-----------------------------------------------------------------------------+ */+#include "postgres.h"++#include "access/csn_log.h"+#include "access/slru.h"+#include "access/csn_snapshot.h"+#include "access/subtrans.h"+#include "access/transam.h"+#include "access/xlogutils.h"+#include "miscadmin.h"+#include "pg_trace.h"+#include "portability/instr_time.h"+#include "storage/shmem.h"+#include "storage/spin.h"+#include "utils/snapmgr.h"+#include "access/xlog_internal.h"++/*+ * We use csnSnapshotActive to judge if csn snapshot enabled instead of by+ * enable_csn_snapshot, this design is similar to 'track_commit_timestamp'.+ *+ * Because in process of replication if master changes 'enable_csn_snapshot'+ * in a database restart, standby should apply wal record for GUC changed,+ * then it's difficult to notice all backends about that. So they can get+ * the message by 'csnSnapshotActive' which in shared buffer. It will not+ * acquire a lock, so without performance issue.+ * last_max_csn - Record the max csn till now.+ * last_csn_log_wal - for interval we log the assign csn to wal+ * oldestXmin - first sensible Xmin on the first existed page in the CSN Log+ */+typedef struct CSNShared+{+ bool csnSnapshotActive;+ pg_atomic_uint32 oldestXmin;+ CSN last_max_csn;+ CSN last_csn_log_wal;+ volatile slock_t lock;+} CSNShared;++CSNShared *csnShared;++/*+ * Defines for CSNLog page sizes. A page is the same BLCKSZ as is used+ * everywhere else in Postgres.+ *+ * Note: because TransactionIds are 32 bits and wrap around at 0xFFFFFFFF,+ * CSNLog page numbering also wraps around at+ * 0xFFFFFFFF/CSN_LOG_XACTS_PER_PAGE, and CSNLog segment numbering at+ * 0xFFFFFFFF/CLOG_XACTS_PER_PAGE/SLRU_PAGES_PER_SEGMENT. We need take no+ * explicit notice of that fact in this module, except when comparing segment+ * and page numbers in TruncateCSNLog (see CSNLogPagePrecedes).+ */++/* We store the commit CSN for each xid */+#define CSN_LOG_XACTS_PER_PAGE (BLCKSZ / sizeof(CSN))++#define TransactionIdToPage(xid) ((xid) / (TransactionId) CSN_LOG_XACTS_PER_PAGE)+#define TransactionIdToPgIndex(xid) ((xid) % (TransactionId) CSN_LOG_XACTS_PER_PAGE)++/*+ * Link to shared-memory data structures for CLOG control+ */+static SlruCtlData CSNLogCtlData;+#define CsnlogCtl (&CSNLogCtlData)++static int ZeroCSNLogPage(int pageno, bool write_xlog);+static void ZeroTruncateCSNLogPage(int pageno, bool write_xlog);+static bool CSNLogPagePrecedes(int page1, int page2);+static void CSNLogSetPageStatus(TransactionId xid, int nsubxids,+ TransactionId *subxids,+ CSN csn, int pageno);+static void CSNLogSetCSNInSlot(TransactionId xid, CSN csn, int slotno);++static void WriteCSNXlogRec(TransactionId xid, int nsubxids,+ TransactionId *subxids, CSN csn);+static void WriteZeroCSNPageXlogRec(int pageno);+static void WriteTruncateCSNXlogRec(int pageno);+static void set_oldest_xmin(TransactionId xid);+++/*+ * Number of shared CSNLog buffers.+ */+static Size+CSNLogShmemBuffers(void)+{+ return Min(32, Max(4, NBuffers / 512));+}++/*+ * Reserve shared memory for CsnlogCtl.+ */+Size+CSNLogShmemSize(void)+{+ return SimpleLruShmemSize(CSNLogShmemBuffers(), 0);+}++/*+ * Initialization of shared memory for CSNLog.+ */+void+CSNLogShmemInit(void)+{+ bool found;++ CsnlogCtl->PagePrecedes = CSNLogPagePrecedes;+ SimpleLruInit(CsnlogCtl, "CSNLog Ctl", CSNLogShmemBuffers(), 0,+ CSNLogSLRULock, "pg_csn", LWTRANCHE_CSN_LOG_BUFFERS,+ SYNC_HANDLER_CSN);++ csnShared = ShmemInitStruct("CSNlog shared",+ sizeof(CSNShared),+ &found);+ if (!found)+ {+ csnShared->csnSnapshotActive = false;+ pg_atomic_init_u32(&csnShared->oldestXmin, InvalidTransactionId);+ csnShared->last_max_csn = InvalidCSN;+ csnShared->last_csn_log_wal = InvalidCSN;+ SpinLockInit(&csnShared->lock);+ }+}++/*+ * CSNLogSetCSN+ *+ * Record CSN of transaction and its subtransaction tree.+ *+ * xid is a single xid to set status for. This will typically be the top level+ * transactionid for a top level commit or abort. It can also be a+ * subtransaction when we record transaction aborts.+ *+ * subxids is an array of xids of length nsubxids, representing subtransactions+ * in the tree of xid. In various cases nsubxids may be zero.+ *+ * csn is the commit sequence number of the transaction. It should be+ * AbortedCSN for abort cases.+ */+void+CSNLogSetCSN(TransactionId xid, int nsubxids, TransactionId *subxids, CSN csn,+ bool write_xlog)+{+ int pageno;+ int i = 0;+ int offset = 0;++ Assert(TransactionIdIsValid(xid));++ pageno = TransactionIdToPage(xid); /* get page of parent */++ if(write_xlog)+ WriteCSNXlogRec(xid, nsubxids, subxids, csn);++ for (;;)+ {+ int num_on_page = 0;++ /* Form subtransactions bucket that can be written on the same page */+ while (i < nsubxids && TransactionIdToPage(subxids[i]) == pageno)+ {+ num_on_page++;+ i++;+ }++ CSNLogSetPageStatus(xid,+ num_on_page, subxids + offset,+ csn, pageno);+ if (i >= nsubxids)+ break;++ offset = i;+ pageno = TransactionIdToPage(subxids[offset]);+ xid = InvalidTransactionId;+ }+}++/*+ * Record the final state of transaction entries in the csn log for+ * all entries on a single page. Atomic only on this page.+ *+ * Otherwise API is same as TransactionIdSetTreeStatus()+ */+static void+CSNLogSetPageStatus(TransactionId xid, int nsubxids, TransactionId *subxids,+ CSN csn, int pageno)+{+ int slotno;+ int i;++ LWLockAcquire(CSNLogSLRULock, LW_EXCLUSIVE);++ slotno = SimpleLruReadPage(CsnlogCtl, pageno, true, xid);++ /* Subtransactions first, if needed ... */+ for (i = 0; i < nsubxids; i++)+ {+ Assert(CsnlogCtl->shared->page_number[slotno] == TransactionIdToPage(subxids[i]));+ CSNLogSetCSNInSlot(subxids[i], csn, slotno);+ }++ /* ... then the main transaction */+ if (TransactionIdIsValid(xid))+ CSNLogSetCSNInSlot(xid, csn, slotno);++ CsnlogCtl->shared->page_dirty[slotno] = true;++ LWLockRelease(CSNLogSLRULock);+}++/*+ * Sets the commit status of a single transaction.+ */+static void+CSNLogSetCSNInSlot(TransactionId xid, CSN csn, int slotno)+{+ int entryno = TransactionIdToPgIndex(xid);+ CSN *ptr;++ Assert(LWLockHeldByMe(CSNLogSLRULock));++ ptr = (CSN *) (CsnlogCtl->shared->page_buffer[slotno] ++ entryno * sizeof(CSN));+ *ptr = csn;+}++/*+ * Interrogate the state of a transaction in the log.+ *+ * NB: this is a low-level routine and is NOT the preferred entry point+ * for most uses; TransactionIdGetCSN() in csn_snapshot.c is the+ * intended caller.+ */+CSN+CSNLogGetCSNByXid(TransactionId xid)+{+ int pageno = TransactionIdToPage(xid);+ int entryno = TransactionIdToPgIndex(xid);+ int slotno;+ CSN csn;++ /* lock is acquired by SimpleLruReadPage_ReadOnly */+ slotno = SimpleLruReadPage_ReadOnly(CsnlogCtl, pageno, xid);+ csn = *(CSN *) (CsnlogCtl->shared->page_buffer[slotno] ++ entryno * sizeof(CSN));+ LWLockRelease(CSNLogSLRULock);++ return csn;+}++/*+ * Initialize (or reinitialize) a page of CSNLog to zeroes.+ *+ * The page is not actually written, just set up in shared memory.+ * The slot number of the new page is returned.+ *+ * Control lock must be held at entry, and will be held at exit.+ */+static int+ZeroCSNLogPage(int pageno, bool write_xlog)+{+ Assert(LWLockHeldByMe(CSNLogSLRULock));+ if(write_xlog)+ WriteZeroCSNPageXlogRec(pageno);+ return SimpleLruZeroPage(CsnlogCtl, pageno);+}++static void+ZeroTruncateCSNLogPage(int pageno, bool write_xlog)+{+ if(write_xlog)+ WriteTruncateCSNXlogRec(pageno);+ SimpleLruTruncate(CsnlogCtl, pageno);+}++void+ActivateCSNlog(void)+{+ int pageno;+ TransactionId nextXid = InvalidTransactionId;+ TransactionId oldest_xid = InvalidTransactionId;++ if (csnShared->csnSnapshotActive)+ return;++ nextXid = XidFromFullTransactionId(ShmemVariableCache->nextXid);+ pageno = TransactionIdToPage(nextXid);++ LWLockAcquire(CSNLogSLRULock, LW_EXCLUSIVE);++ /*+ * Create the current segment file, if necessary.+ * This means that+ */+ if (!SimpleLruDoesPhysicalPageExist(CsnlogCtl, pageno))+ {+ int slotno;+ TransactionId curxid = nextXid;++ slotno = ZeroCSNLogPage(pageno, false);+ SimpleLruWritePage(CsnlogCtl, slotno);++ elog(LOG, "Create SLRU page=%d, slotno=%d for xid %u on a CSN log activation",+ pageno, slotno, nextXid);++ /*+ * nextXid isn't first xid on the page. It is the first page in the CSN+ * log. Set UnclearCSN value into all previous slots on this page.+ * This xid value can be used as an oldest xid in the CSN log.+ */+ if (TransactionIdToPgIndex(nextXid) > 0)+ {+ /* Cleaning procedure. Can be optimized. */+ do+ {+ curxid--;+ CSNLogSetCSNInSlot(curxid, UnclearCSN, slotno);+ } while (TransactionIdToPgIndex(curxid) > 0);++ elog(LOG,+ "Set UnclearCSN values for %d xids in the range [%u,%u]",+ nextXid - curxid, curxid, nextXid-1);++ /* Oldest XID found on this page */+ oldest_xid = nextXid;+ }+ }+ LWLockRelease(CSNLogSLRULock);++ if (!TransactionIdIsValid(oldest_xid))+ {+ TransactionId curxid;++ elog(LOG, "Search for the oldest xid across previous pages");++ /* Need to scan previous pages for an oldest xid. */+ while (pageno > 0 && SimpleLruDoesPhysicalPageExist(CsnlogCtl, pageno - 1))+ pageno--;++ /* look up for the first clear xid value. */+ curxid = pageno * (TransactionId) CSN_LOG_XACTS_PER_PAGE;+ while(CSNLogGetCSNByXid(curxid) == UnclearCSN)+ curxid++;+ oldest_xid = curxid;+ }++ set_oldest_xmin(oldest_xid);+ csnShared->csnSnapshotActive = true;+}++bool+get_csnlog_status(void)+{+ return csnShared->csnSnapshotActive;+}++void+DeactivateCSNlog(void)+{+ csnShared->csnSnapshotActive = false;+ set_oldest_xmin(InvalidTransactionId);+ LWLockAcquire(CSNLogSLRULock, LW_EXCLUSIVE);+ (void) SlruScanDirectory(CsnlogCtl, SlruScanDirCbDeleteAll, NULL);+ LWLockRelease(CSNLogSLRULock);+ elog(LOG, "CSN log has deactivated");+}++void+StartupCSN(void)+{+ ActivateCSNlog();+}++void+CompleteCSNInitialization(void)+{+ /*+ * If the feature is not enabled, turn it off for good. This also removes+ * any leftover data.+ *+ * Conversely, we activate the module if the feature is enabled. This is+ * necessary for primary and standby as the activation depends on the+ * control file contents at the beginning of recovery or when a+ * XLOG_PARAMETER_CHANGE is replayed.+ */+ if (!enable_csn_snapshot)+ DeactivateCSNlog();+ else+ ActivateCSNlog();+}++void+CSNlogParameterChange(bool newvalue, bool oldvalue)+{+ if (newvalue)+ {+ if (!csnShared->csnSnapshotActive)+ ActivateCSNlog();+ }+ else if (csnShared->csnSnapshotActive)+ DeactivateCSNlog();+}++/*+ * Perform a checkpoint --- either during shutdown, or on-the-fly+ */+void+CheckPointCSNLog(void)+{+ if (!get_csnlog_status())+ return;++ /*+ * Flush dirty CSNLog pages to disk.+ *+ * This is not actually necessary from a correctness point of view. We do+ * it merely to improve the odds that writing of dirty pages is done by+ * the checkpoint process and not by backends.+ */+ TRACE_POSTGRESQL_CSNLOG_CHECKPOINT_START(true);+ SimpleLruWriteAll(CsnlogCtl, true);+ TRACE_POSTGRESQL_CSNLOG_CHECKPOINT_DONE(true);+}++/*+ * Make sure that CSNLog has room for a newly-allocated XID.+ *+ * NB: this is called while holding XidGenLock. We want it to be very fast+ * most of the time; even when it's not so fast, no actual I/O need happen+ * unless we're forced to write out a dirty clog or xlog page to make room+ * in shared memory.+ */+void+ExtendCSNLog(TransactionId newestXact)+{+ int pageno;++ if (!get_csnlog_status())+ return;++ /*+ * No work except at first XID of a page. But beware: just after+ * wraparound, the first XID of page zero is FirstNormalTransactionId.+ */+ if (TransactionIdToPgIndex(newestXact) != 0 &&+ !TransactionIdEquals(newestXact, FirstNormalTransactionId))+ return;++ pageno = TransactionIdToPage(newestXact);++ LWLockAcquire(CSNLogSLRULock, LW_EXCLUSIVE);++ /* Zero the page and make an XLOG entry about it */+ ZeroCSNLogPage(pageno, !InRecovery);++ LWLockRelease(CSNLogSLRULock);+}++/*+ * Remove all CSNLog segments before the one holding the passed+ * transaction ID.+ *+ * This is normally called during checkpoint, with oldestXact being the+ * oldest TransactionXmin of any running transaction.+ */+void+TruncateCSNLog(TransactionId oldestXact)+{+ int cutoffPage;+ TransactionId oldestXmin;++ /* Can't do truncation because WAL messages isn't allowed during recovery */+ if (RecoveryInProgress() || !get_csnlog_status())+ return;++ /*+ * The cutoff point is the start of the segment containing oldestXact. We+ * pass the *page* containing oldestXact to SimpleLruTruncate. We step+ * back one transaction to avoid passing a cutoff page that hasn't been+ * created yet in the rare case that oldestXact would be the first item on+ * a page and oldestXact == next XID. In that case, if we didn't subtract+ * one, we'd trigger SimpleLruTruncate's wraparound detection.+ */+ TransactionIdRetreat(oldestXact);+ cutoffPage = TransactionIdToPage(oldestXact);++ /* Detect, that we really need to cut CSN log. */+ oldestXmin = pg_atomic_read_u32(&csnShared->oldestXmin);++ if (TransactionIdToPage(oldestXmin) < cutoffPage)+ {+ /* OldestXact is located in the same page as oldestXmin. No actions needed. */+ return;+ }++ /*+ * Shift oldestXmin to the start of new first page. Use first position+ * on the page because all transactions on this page is created with enabled+ * CSN snapshot machinery.+ */+ pg_atomic_write_u32(&csnShared->oldestXmin,+ oldestXact - TransactionIdToPgIndex(oldestXact));++ SpinLockRelease(&csnShared->lock);+ ZeroTruncateCSNLogPage(cutoffPage, true);+}++/*+ * Decide which of two CSNLog page numbers is "older" for truncation+ * purposes.+ *+ * We need to use comparison of TransactionIds here in order to do the right+ * thing with wraparound XID arithmetic. However, if we are asked about+ * page number zero, we don't want to hand InvalidTransactionId to+ * TransactionIdPrecedes: it'll get weird about permanent xact IDs. So,+ * offset both xids by FirstNormalTransactionId to avoid that.+ */+static bool+CSNLogPagePrecedes(int page1, int page2)+{+ TransactionId xid1;+ TransactionId xid2;++ xid1 = ((TransactionId) page1) * CSN_LOG_XACTS_PER_PAGE;+ xid1 += FirstNormalTransactionId;+ xid2 = ((TransactionId) page2) * CSN_LOG_XACTS_PER_PAGE;+ xid2 += FirstNormalTransactionId;++ return TransactionIdPrecedes(xid1, xid2);+}++void+WriteAssignCSNXlogRec(CSN csn)+{+ Assert(enable_csn_wal && csn <= csnShared->last_csn_log_wal);++ XLogBeginInsert();+ XLogRegisterData((char *) (&csn), sizeof(CSN));+ XLogInsert(RM_CSNLOG_ID, XLOG_CSN_ASSIGNMENT);+}++static void+WriteCSNXlogRec(TransactionId xid, int nsubxids,+ TransactionId *subxids, CSN csn)+{+ xl_csn_set xlrec;++ if(!enable_csn_wal)+ return;++ xlrec.xtop = xid;+ xlrec.nsubxacts = nsubxids;+ xlrec.csn = csn;++ XLogBeginInsert();+ XLogRegisterData((char *) &xlrec, MinSizeOfCSNSet);+ XLogRegisterData((char *) subxids, nsubxids * sizeof(TransactionId));+ XLogInsert(RM_CSNLOG_ID, XLOG_CSN_SETCSN);+}++/*+ * Write a ZEROPAGE xlog record+ */+static void+WriteZeroCSNPageXlogRec(int pageno)+{+ if(!enable_csn_wal)+ {+ return;+ }+ XLogBeginInsert();+ XLogRegisterData((char *) (&pageno), sizeof(int));+ (void) XLogInsert(RM_CSNLOG_ID, XLOG_CSN_ZEROPAGE);+}++/*+ * Write a TRUNCATE xlog record+ */+static void+WriteTruncateCSNXlogRec(int pageno)+{+ if(!enable_csn_wal)+ {+ return;+ }+ XLogBeginInsert();+ XLogRegisterData((char *) (&pageno), sizeof(int));+ XLogInsert(RM_CSNLOG_ID, XLOG_CSN_TRUNCATE);+}+++void+csnlog_redo(XLogReaderState *record)+{+ uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;++ /* Backup blocks are not used in csnlog records */+ Assert(!XLogRecHasAnyBlockRefs(record));++ if (info == XLOG_CSN_ASSIGNMENT)+ {+ CSN csn;++ memcpy(&csn, XLogRecGetData(record), sizeof(CSN));+ /* XXX: Do we really not needed to acquire the lock here? */+ csnShared->last_max_csn = csn;+ }+ else if (info == XLOG_CSN_SETCSN)+ {+ xl_csn_set *xlrec = (xl_csn_set *) XLogRecGetData(record);+ CSNLogSetCSN(xlrec->xtop, xlrec->nsubxacts, xlrec->xsub, xlrec->csn, false);+ }+ else if (info == XLOG_CSN_ZEROPAGE)+ {+ int pageno;+ int slotno;++ memcpy(&pageno, XLogRecGetData(record), sizeof(int));+ LWLockAcquire(CSNLogSLRULock, LW_EXCLUSIVE);+ slotno = ZeroCSNLogPage(pageno, false);+ SimpleLruWritePage(CsnlogCtl, slotno);+ LWLockRelease(CSNLogSLRULock);+ Assert(!CsnlogCtl->shared->page_dirty[slotno]);++ }+ else if (info == XLOG_CSN_TRUNCATE)+ {+ int pageno;++ memcpy(&pageno, XLogRecGetData(record), sizeof(int));+ CsnlogCtl->shared->latest_page_number = pageno;+ ZeroTruncateCSNLogPage(pageno, false);+ }+ else+ elog(PANIC, "csnlog_redo: unknown op code %u", info);+}++/*+ * Entrypoint for sync.c to sync members files.+ */+int+csnsyncfiletag(const FileTag *ftag, char *path)+{+ return SlruSyncFileTag(&CSNLogCtlData, ftag, path);+}++/*+ * GenerateCSN+ *+ * Generate CSN which is actually a local time. Also we are forcing+ * this time to be always increasing. Since now it is not uncommon to have+ * millions of read transactions per second we are trying to use nanoseconds+ * if such time resolution is available.+ */+CSN+GenerateCSN(bool locked, CSN assign)+{+ instr_time current_time;+ CSN csn;+ CSN log_csn = InvalidCSN;++ Assert(get_csnlog_status() || csn_snapshot_defer_time > 0);++ /* TODO: create some macro that add small random shift to current time. */+ INSTR_TIME_SET_CURRENT(current_time);+ csn = (CSN) INSTR_TIME_GET_NANOSEC(current_time) + (int64) (csn_time_shift * 1E9);++ if(assign != InvalidCSN && csn < assign)+ csn = assign;++ /* TODO: change to atomics? */+ if (!locked)+ SpinLockAcquire(&csnShared->lock);++ if (csn <= csnShared->last_max_csn)+ csn = csnShared->last_max_csn + 1;+ csnShared->last_max_csn = csn;++ if (enable_csn_wal && csn > csnShared->last_csn_log_wal)+ {+ /*+ * We log the CSN 5s greater than generated, you can see comments on+ * the CSN_ASSIGN_TIME_INTERVAL.+ */+ log_csn = CSNAddByNanosec(csn, CSN_ASSIGN_TIME_INTERVAL);+ csnShared->last_csn_log_wal = log_csn;+ }++ if (!locked)+ SpinLockRelease(&csnShared->lock);++ if (log_csn != InvalidCSN)+ WriteAssignCSNXlogRec(csn);++ return csn;+}++CSN+GetLastGeneratedCSN(void)+{+ CSN csn;++ SpinLockAcquire(&csnShared->lock);+ csn = csnShared->last_max_csn;+ SpinLockRelease(&csnShared->lock);+ return csn;+}++/*+ * Mostly for debug purposes.+ */+static void+set_oldest_xmin(TransactionId xid)+{+ elog(LOG, "Oldest Xmin for CSN will be changed from %u to %u",+ pg_atomic_read_u32(&csnShared->oldestXmin), xid);++ pg_atomic_write_u32(&csnShared->oldestXmin, xid);+}++TransactionId+GetOldestXmin(void)+{+ Assert(get_csnlog_status());+ return pg_atomic_read_u32(&csnShared->oldestXmin);+}diff --git a/src/backend/access/transam/csn_snapshot.c b/src/backend/access/transam/csn_snapshot.cnew file mode 100644index 0000000000..a381d219ea--- /dev/null+++ b/src/backend/access/transam/csn_snapshot.c@@ -0,0 +1,687 @@+/*-------------------------------------------------------------------------+ *+ * csn_snapshot.c+ * Support for cross-node snapshot isolation.+ *+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group+ * Portions Copyright (c) 1994, Regents of the University of California+ *+ * src/backend/access/transam/csn_snapshot.c+ *+ *-------------------------------------------------------------------------+ */+#include "postgres.h"++#include "access/csn_snapshot.h"+#include "access/subtrans.h"+#include "access/transam.h"+#include "access/twophase.h"+#include "access/xact.h"+#include "portability/instr_time.h"+#include "storage/lmgr.h"+#include "storage/proc.h"+#include "storage/procarray.h"+#include "storage/shmem.h"+#include "storage/spin.h"+#include "utils/builtins.h"+#include "utils/guc.h"+#include "utils/snapmgr.h"+#include "miscadmin.h"++/* Raise a warning if imported snapshot_csn exceeds ours by this value. */+#define SNAP_DESYNC_COMPLAIN (1*NSECS_PER_SEC) /* 1 second */++static TransactionId xmin_for_csn = InvalidTransactionId;+++/*+ * GUC to delay advance of oldestXid for this amount of time. Also determines+ * the size CSNSnapshotXidMap circular buffer.+ */+int csn_snapshot_defer_time;++int csn_time_shift;++/*+ * CSNSnapshotXidMap+ *+ * To be able to install csn snapshot that points to past we need to keep+ * old versions of tuples and therefore delay advance of oldestXid. Here we+ * keep track of correspondence between snapshot's snapshot_csn and oldestXid+ * that was set at the time when the snapshot was taken. Much like the+ * snapshot too old's OldSnapshotControlData does, but with finer granularity+ * to seconds.+ *+ * Different strategies can be employed to hold oldestXid (e.g. we can track+ * oldest csn-based snapshot among cluster nodes and map it oldestXid+ * on each node).+ *+ * On each snapshot acquisition CSNSnapshotMapXmin() is called and stores+ * correspondence between current snapshot_csn and oldestXmin in a sparse way:+ * snapshot_csn is rounded to seconds (and here we use the fact that snapshot_csn+ * is just a timestamp) and oldestXmin is stored in the circular buffer where+ * rounded snapshot_csn acts as an offset from current circular buffer head.+ * Size of the circular buffer is controlled by csn_snapshot_defer_time GUC.+ *+ * When csn snapshot arrives we check that its+ * snapshot_csn is still in our map, otherwise we'll error out with "snapshot too+ * old" message. If snapshot_csn is successfully mapped to oldestXid we move+ * backend's pgxact->xmin to proc->originalXmin and fill pgxact->xmin to+ * mapped oldestXid. That way GetOldestXmin() can take into account backends+ * with imported csn snapshot and old tuple versions will be preserved.+ *+ * Also while calculating oldestXmin for our map in presence of imported+ * csn snapshots we should use proc->originalXmin instead of pgxact->xmin+ * that was set during import. Otherwise, we can create a feedback loop:+ * xmin's of imported csn snapshots were calculated using our map and new+ * entries in map going to be calculated based on that xmin's, and there is+ * a risk to stuck forever with one non-increasing oldestXmin. All other+ * callers of GetOldestXmin() are using pgxact->xmin so the old tuple versions+ * are preserved.+ */+typedef struct CSNSnapshotXidMap+{+ int head; /* offset of current freshest value */+ int size; /* total size of circular buffer */+ CSN_atomic last_csn_seconds; /* last rounded csn that changed+ * xmin_by_second[] */+ TransactionId *xmin_by_second; /* circular buffer of oldestXmin's */+}+CSNSnapshotXidMap;++static CSNSnapshotXidMap *csnXidMap;+++/* Estimate shared memory space needed */+Size+CSNSnapshotShmemSize(void)+{+ Size size = 0;++ if (csn_snapshot_defer_time > 0)+ {+ size += sizeof(CSNSnapshotXidMap);+ size += csn_snapshot_defer_time*sizeof(TransactionId);+ size = MAXALIGN(size);+ }++ return size;+}++/* Init shared memory structures */+void+CSNSnapshotShmemInit()+{+ bool found;++ if (csn_snapshot_defer_time > 0)+ {+ csnXidMap = ShmemInitStruct("csnXidMap",+ sizeof(CSNSnapshotXidMap),+ &found);+ if (!found)+ {+ int i;++ pg_atomic_init_u64(&csnXidMap->last_csn_seconds, 0);+ csnXidMap->head = 0;+ csnXidMap->size = csn_snapshot_defer_time;+ csnXidMap->xmin_by_second =+ ShmemAlloc(sizeof(TransactionId)*csnXidMap->size);++ for (i = 0; i < csnXidMap->size; i++)+ csnXidMap->xmin_by_second[i] = InvalidTransactionId;+ }+ }+}++/*+ * CSNSnapshotStartup+ *+ * Set csnXidMap entries to oldestActiveXID during startup.+ */+void+CSNSnapshotStartup(TransactionId oldestActiveXID)+{+ /*+ * Run only if we have initialized shared memory and csnXidMap+ * is enabled.+ */+ if (IsNormalProcessingMode() &&+ enable_csn_snapshot && csn_snapshot_defer_time > 0)+ {+ int i;++ Assert(TransactionIdIsValid(oldestActiveXID));+ for (i = 0; i < csnXidMap->size; i++)+ csnXidMap->xmin_by_second[i] = oldestActiveXID;+ ProcArraySetCSNSnapshotXmin(oldestActiveXID);++ elog(LOG, "CSN map initialized with oldest active xid %u", oldestActiveXID);+ }+}++/*+ * CSNSnapshotMapXmin+ *+ * Maintain circular buffer of oldestXmins for several seconds in past. This+ * buffer allows to shift oldestXmin in the past when backend is importing+ * CSN snapshot. Otherwise old versions of tuples that were needed for+ * this transaction can be recycled by other processes (vacuum, HOT, etc).+ *+ * Locking here is not trivial. Called upon each snapshot creation after+ * ProcArrayLock is released. Such usage creates several race conditions. It+ * is possible that backend who got csn called CSNSnapshotMapXmin()+ * only after other backends managed to get snapshot and complete+ * CSNSnapshotMapXmin() call, or even committed. This is safe because+ *+ * * We already hold our xmin in MyPgXact, so our snapshot will not be+ * harmed even though ProcArrayLock is released.+ *+ * * snapshot_csn is always pessmistically rounded up to the next+ * second.+ *+ * * For performance reasons, xmin value for particular second is filled+ * only once. Because of that instead of writing to buffer just our+ * xmin (which is enough for our snapshot), we bump oldestXmin there --+ * it mitigates the possibility of damaging someone else's snapshot by+ * writing to the buffer too advanced value in case of slowness of+ * another backend who generated csn earlier, but didn't manage to+ * insert it before us.+ *+ * * if CSNSnapshotMapXmin() founds a gap in several seconds between+ * current call and latest completed call then it should fill that gap+ * with latest known values instead of new one. Otherwise it is+ * possible (however highly unlikely) that this gap also happend+ * between taking snapshot and call to CSNSnapshotMapXmin() for some+ * backend. And we are at risk to fill circullar buffer with+ * oldestXmin's that are bigger then they actually were.+ */+void+CSNSnapshotMapXmin(SnapshotCSN snapshot_csn)+{+ int offset, gap, i;+ SnapshotCSN csn_seconds;+ SnapshotCSN last_csn_seconds;+ volatile TransactionId oldest_deferred_xmin;+ TransactionId current_oldest_xmin, previous_oldest_xmin;+ TransactionId ImportedXmin;++ /* Callers should check config values */+ Assert(csn_snapshot_defer_time > 0);+ Assert(csnXidMap != NULL);+ /*+ * Round up snapshot_csn to the next second -- pessimistically and safely.+ */+ csn_seconds = (snapshot_csn / NSECS_PER_SEC + 1);++ /*+ * Fast-path check. Avoid taking exclusive CSNSnapshotXidMapLock lock+ * if oldestXid was already written to xmin_by_second[] for this rounded+ * snapshot_csn.+ */+ if (pg_atomic_read_u64(&csnXidMap->last_csn_seconds) >= csn_seconds)+ return;++ /* Ok, we have new entry (or entries) */+ LWLockAcquire(CSNSnapshotXidMapLock, LW_EXCLUSIVE);++ /* Re-check last_csn_seconds under lock */+ last_csn_seconds = pg_atomic_read_u64(&csnXidMap->last_csn_seconds);+ if (last_csn_seconds >= csn_seconds)+ {+ LWLockRelease(CSNSnapshotXidMapLock);+ return;+ }+ pg_atomic_write_u64(&csnXidMap->last_csn_seconds, csn_seconds);++ /*+ * Count oldest_xmin.+ *+ * It was possible to calculate oldest_xmin during corresponding snapshot+ * creation, but GetSnapshotData() intentionally reads only PgXact, but not+ * PgProc. And we need info about originalXmin (see comment to csnXidMap)+ * which is stored in PgProc because of threats in comments around PgXact+ * about extending it with new fields. So just calculate oldest_xmin again,+ * that anyway happens quite rarely.+ */++ /*+ * Don't afraid here because csn_snapshot_xmin will hold border of+ * minimal non-removable from vacuuming.+ */+ ImportedXmin = MyProc->xmin;+ MyProc->xmin = MyProc->originalXmin;+ current_oldest_xmin = GetOldestNonRemovableTransactionId(NULL);+ MyProc->xmin = ImportedXmin;+ Assert(TransactionIdIsNormal(current_oldest_xmin));++ previous_oldest_xmin = csnXidMap->xmin_by_second[csnXidMap->head];+ Assert(TransactionIdIsNormal(previous_oldest_xmin) || !enable_csn_snapshot);++ gap = csn_seconds - last_csn_seconds;+ offset = csn_seconds % csnXidMap->size;++ /* Sanity check before we update head and gap */+ Assert( gap >= 1 );+ Assert( (csnXidMap->head + gap) % csnXidMap->size == offset );++ gap = gap > csnXidMap->size ? csnXidMap->size : gap;+ csnXidMap->head = offset;++ /* Fill new entry with current_oldest_xmin */+ csnXidMap->xmin_by_second[offset] = current_oldest_xmin;++ /*+ * If we have gap then fill it with previous_oldest_xmin for reasons+ * outlined in comment above this function.+ */+ for (i = 1; i < gap; i++)+ {+ offset = (offset + csnXidMap->size - 1) % csnXidMap->size;+ csnXidMap->xmin_by_second[offset] = previous_oldest_xmin;+ }++ oldest_deferred_xmin =+ csnXidMap->xmin_by_second[ (csnXidMap->head + 1) % csnXidMap->size ];++ LWLockRelease(CSNSnapshotXidMapLock);++ elog(DEBUG5, "Advance xmin for CSN. Oldest deferred xmin = %u",+ oldest_deferred_xmin);++ /*+ * Advance procArray->csn_snapshot_xmin after we released+ * CSNSnapshotXidMapLock. Since we gather not xmin but oldestXmin, it+ * never goes backwards regardless of how slow we can do that.+ */+ /*Assert(TransactionIdFollowsOrEquals(oldest_deferred_xmin,+ ProcArrayGetCSNSnapshotXmin()));*/+ ProcArraySetCSNSnapshotXmin(oldest_deferred_xmin);+}+++/*+ * CSNSnapshotToXmin+ *+ * Get oldestXmin that took place when snapshot_csn was taken.+ */+TransactionId+CSNSnapshotToXmin(SnapshotCSN snapshot_csn)+{+ TransactionId xmin;+ SnapshotCSN csn_seconds;+ volatile SnapshotCSN last_csn_seconds;++ /* Callers should check config values */+ Assert(csn_snapshot_defer_time > 0);+ Assert(csnXidMap != NULL);++ /* Round down to get conservative estimates */+ csn_seconds = (snapshot_csn / NSECS_PER_SEC);++ LWLockAcquire(CSNSnapshotXidMapLock, LW_SHARED);+ last_csn_seconds = pg_atomic_read_u64(&csnXidMap->last_csn_seconds);+ if (csn_seconds > last_csn_seconds)+ {+ /* we don't have entry for this snapshot_csn yet, return latest known */+ xmin = csnXidMap->xmin_by_second[csnXidMap->head];+ }+ else if (last_csn_seconds - csn_seconds < csnXidMap->size)+ {+ /* we are good, retrieve value from our map */+ Assert(last_csn_seconds % csnXidMap->size == csnXidMap->head);+ xmin = csnXidMap->xmin_by_second[csn_seconds % csnXidMap->size];+ }+ else+ {+ /* requested snapshot_csn is too old, let caller know */+ xmin = InvalidTransactionId;+ }+ LWLockRelease(CSNSnapshotXidMapLock);++ return xmin;+}++/*+ * CSNSnapshotPrepareCurrent+ *+ * Set InDoubt state for currently active transaction and return commit's+ * global snapshot.+ */+SnapshotCSN+CSNSnapshotPrepareCurrent(void)+{+ TransactionId xid = GetCurrentTransactionIdIfAny();++ if (!enable_csn_snapshot)+ ereport(ERROR,+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),+ errmsg("could not prepare transaction for global commit"),+ errhint("Make sure the configuration parameter \"%s\" is enabled.",+ "enable_csn_snapshot")));++ if (TransactionIdIsValid(xid))+ {+ TransactionId *subxids;+ int nsubxids = xactGetCommittedChildren(&subxids);+ CSNLogSetCSN(xid, nsubxids, subxids, InDoubtCSN, true);+ }++ /* Nothing to write if we don't have xid */++ return GenerateCSN(false, InvalidCSN);+}+++/*+ * CSNSnapshotAssignCurrent+ *+ * Assign SnapshotCSN to the currently active transaction. SnapshotCSN is supposedly+ * maximal among of values returned by CSNSnapshotPrepareCurrent and+ * pg_csn_snapshot_prepare.+ */+void+CSNSnapshotAssignCurrent(SnapshotCSN snapshot_csn)+{+ if (!enable_csn_snapshot)+ ereport(ERROR,+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),+ errmsg("could not prepare transaction for global commit"),+ errhint("Make sure the configuration parameter \"%s\" is enabled.",+ "enable_csn_snapshot")));++ if (!CSNIsNormal(snapshot_csn))+ ereport(ERROR,+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),+ errmsg("pg_csn_snapshot_assign expects normal snapshot_csn")));++ Assert(snapshot_csn != InvalidCSN);+ /* We do not care the Generate result, we just want to make sure max+ * csnShared->last_max_csn value.+ */+ GenerateCSN(false, snapshot_csn);++ /* Set csn and defuse ProcArrayEndTransaction from assigning one */+ pg_atomic_write_u64(&MyProc->assignedCSN, snapshot_csn);+}++/*+ * CSNSnapshotSync+ *+ * Due to time desynchronization on different nodes we can receive snapshot_csn+ * which is greater than snapshot_csn on this node. To preserve proper isolation+ * this node needs to wait when such snapshot_csn comes on local clock.+ *+ * This should happend relatively rare if nodes have running NTP/PTP/etc.+ * Complain if wait time is more than SNAP_SYNC_COMPLAIN.+ */+void+CSNSnapshotSync(SnapshotCSN remote_csn)+{+ SnapshotCSN local_csn;+ SnapshotCSN delta;++ Assert(enable_csn_snapshot);++ for(;;)+ {+ if (GetLastGeneratedCSN() > remote_csn)+ return;++ local_csn = GenerateCSN(true, InvalidCSN);++ if (local_csn >= remote_csn)+ /*+ * Everything is fine too, but last_max_csn wasn't updated for+ * some time.+ */+ return;++ /* Okay we need to sleep now */+ delta = remote_csn - local_csn;+ if (delta > SNAP_DESYNC_COMPLAIN)+ ereport(WARNING,+ (errmsg("remote global snapshot exceeds ours by more than a second"),+ errhint("Consider running NTPd on servers participating in global transaction")));++ /* TODO: report this sleeptime somewhere? */+ pg_usleep((long) (delta/NSECS_PER_USEC));++ /*+ * Loop that checks to ensure that we actually slept for specified+ * amount of time.+ */+ }++ Assert(false); /* Should not happend */+ return;+}++/*+ * TransactionIdGetCSN+ *+ * Get CSN for specified TransactionId taking care about special xids,+ * xids beyond TransactionXmin and InDoubt states.+ */+CSN+TransactionIdGetCSN(TransactionId xid)+{+ CSN csn;++ /* Handle permanent TransactionId's for which we don't have mapping */+ if (!TransactionIdIsNormal(xid))+ {+ if (xid == InvalidTransactionId)+ return AbortedCSN;+ if (xid == FrozenTransactionId || xid == BootstrapTransactionId)+ return FrozenCSN;+ Assert(false); /* Should not happend */+ }++ /*+ * If we just switch a xid-snapsot to a csn_snapshot, we should handle a start+ * xid for csn base check. Just in case we have prepared transaction which+ * hold the TransactionXmin but without CSN.+ */+ xmin_for_csn = GetOldestXmin();++ /*+ * For the xid with 'xid >= TransactionXmin and xid < xmin_for_csn',+ * it defined as unclear csn which follow xid-snapshot result.+ */+ if(!TransactionIdPrecedes(xid, TransactionXmin) &&+ TransactionIdPrecedes(xid, xmin_for_csn))+ {+ elog(LOG, "UnclearCSN was returned. xid=%u, TransactionXmin=%u, xmin_for_csn=%u",+ xid, TransactionXmin, xmin_for_csn);+ return UnclearCSN;+ }+ /*+ * For xids which less then TransactionXmin CSNLog can be already+ * trimmed but we know that such transaction is definitely not concurrently+ * running according to any snapshot including timetravel ones. Callers+ * should check TransactionDidCommit after.+ */+ if (TransactionIdPrecedes(xid, TransactionXmin))+ return FrozenCSN;++ /* Read CSN from SLRU */+ csn = CSNLogGetCSNByXid(xid);++ /*+ * If we faced InDoubt state then transaction is being committed and we+ * should wait until CSN will be assigned so that visibility check+ * could decide whether tuple is in snapshot. See also comments in+ * CSNSnapshotPrecommit().+ */+ if (CSNIsInDoubt(csn))+ {+ XactLockTableWait(SubTransGetTopmostTransaction(xid), NULL, NULL, XLTW_None);+ csn = CSNLogGetCSNByXid(xid);+ Assert(CSNIsNormal(csn) || CSNIsAborted(csn));+ }++ Assert(CSNIsNormal(csn) || CSNIsInProgress(csn) || CSNIsAborted(csn));+ return csn;+}++/*+ * XidInCSNSnapshot+ *+ * Version of XidInMVCCSnapshot for transactions. For non-imported+ * csn snapshots this should give same results as XidInLocalMVCCSnapshot+ * (except that aborts will be shown as invisible without going to clog) and to+ * ensure such behaviour XidInMVCCSnapshot is coated with asserts that checks+ * identicalness of XidInCSNSnapshot/XidInLocalMVCCSnapshot in+ * case of ordinary snapshot.+ */+bool+XidInCSNSnapshot(TransactionId xid, Snapshot snapshot)+{+ CSN csn;++ csn = TransactionIdGetCSN(xid);++ if (CSNIsNormal(csn))+ return (csn >= snapshot->snapshot_csn);+ else if (CSNIsFrozen(csn))+ {+ /* It is bootstrap or frozen transaction */+ return false;+ }+ else if(CSNIsUnclear(csn))+ {+ /*+ * Some xid can not figure out csn because of snapshot switch,+ * and we can follow xid-base result.+ */+ return true;+ }+ else+ {+ /* It is aborted or in-progress */+ Assert(CSNIsAborted(csn) || CSNIsInProgress(csn));+ if (CSNIsAborted(csn))+ Assert(TransactionIdDidAbort(xid));+ return true;+ }+}+++/*****************************************************************************+ * Functions to handle transactions commit.+ *+ * For local transactions CSNSnapshotPrecommit sets InDoubt state before+ * ProcArrayEndTransaction is called and transaction data potetntially becomes+ * visible to other backends. ProcArrayEndTransaction (or ProcArrayRemove in+ * twophase case) then acquires csn under ProcArray lock and stores it+ * in proc->assignedCSN. It's important that csn for commit is+ * generated under ProcArray lock, otherwise snapshots won't+ * be equivalent. Consequent call to CSNSnapshotCommit will write+ * proc->assignedCSN to CSNLog.+ *+ *+ * CSNSnapshotAbort is slightly different comparing to commit because abort+ * can skip InDoubt phase and can be called for transaction subtree.+ *****************************************************************************/+++/*+ * CSNSnapshotAbort+ *+ * Abort transaction in CsnLog. We can skip InDoubt state for aborts+ * since no concurrent transactions allowed to see aborted data anyway.+ */+void+CSNSnapshotAbort(PGPROC *proc, TransactionId xid,+ int nsubxids, TransactionId *subxids)+{+ if (!get_csnlog_status())+ return;++ CSNLogSetCSN(xid, nsubxids, subxids, AbortedCSN, true);++ /*+ * Clean assignedCSN anyway, as it was possibly set in+ * XidSnapshotAssignCsnCurrent.+ */+ pg_atomic_write_u64(&proc->assignedCSN, InProgressCSN);+}++/*+ * CSNSnapshotPrecommit+ *+ * Set InDoubt status for local transaction that we are going to commit.+ * This step is needed to achieve consistency between local snapshots and+ * csn-based snapshots. We don't hold ProcArray lock while writing+ * csn for transaction in SLRU but instead we set InDoubt status before+ * transaction is deleted from ProcArray so the readers who will read csn+ * in the gap between ProcArray removal and CSN assignment can wait+ * until CSN is finally assigned. See also TransactionIdGetCSN().+ *+ * This should be called only from parallel group leader before backend is+ * deleted from ProcArray.+ */+void+CSNSnapshotPrecommit(PGPROC *proc, TransactionId xid,+ int nsubxids, TransactionId *subxids)+{+ CSN oldassignedCSN = InProgressCSN;+ bool in_progress;++ if (!get_csnlog_status())+ return;++ /* Set InDoubt status if it is local transaction */+ in_progress = pg_atomic_compare_exchange_u64(&proc->assignedCSN,+ &oldassignedCSN,+ InDoubtCSN);+ if (in_progress)+ {+ Assert(CSNIsInProgress(oldassignedCSN));+ CSNLogSetCSN(xid, nsubxids, subxids, InDoubtCSN, true);+ }+ else+ {+ /* Otherwise we should have valid CSN by this time */+ Assert(CSNIsNormal(oldassignedCSN));+ Assert(CSNIsInDoubt(CSNLogGetCSNByXid(xid)));+ }+}++/*+ * CSNSnapshotCommit+ *+ * Write CSN that were acquired earlier to CsnLog. Should be+ * preceded by CSNSnapshotPrecommit() so readers can wait until we finally+ * finished writing to SLRU.+ *+ * Should be called after ProcArrayEndTransaction, but before releasing+ * transaction locks, so that TransactionIdGetCSN can wait on this+ * lock for CSN.+ */+void+CSNSnapshotCommit(PGPROC *proc, TransactionId xid,+ int nsubxids, TransactionId *subxids)+{+ volatile CSN assignedCSN;++ if (!get_csnlog_status())+ return;++ if (!TransactionIdIsValid(xid))+ {+ assignedCSN = pg_atomic_read_u64(&proc->assignedCSN);+ Assert(CSNIsInProgress(assignedCSN));+ return;+ }++ /* Finally write resulting CSN in SLRU */+ assignedCSN = pg_atomic_read_u64(&proc->assignedCSN);+ Assert(CSNIsNormal(assignedCSN));+ CSNLogSetCSN(xid, nsubxids, subxids, assignedCSN, true);++ /* Reset for next transaction */+ pg_atomic_write_u64(&proc->assignedCSN, InProgressCSN);+}diff --git a/src/backend/access/transam/rmgr.c b/src/backend/access/transam/rmgr.cindex 58091f6b52..b86c172e46 100644--- a/src/backend/access/transam/rmgr.c+++ b/src/backend/access/transam/rmgr.c@@ -10,6 +10,7 @@
#include "access/brin_xlog.h"
#include "access/clog.h"
#include "access/commit_ts.h"
+#include "access/csn_log.h"
#include "access/generic_xlog.h"
#include "access/ginxlog.h"
#include "access/gistxlog.h"
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.cindex 28b153abc3..7bc6aae9a4 100644--- a/src/backend/access/transam/twophase.c+++ b/src/backend/access/transam/twophase.c@@ -77,6 +77,7 @@
#include <unistd.h>
#include "access/commit_ts.h"
+#include "access/csn_snapshot.h"
#include "access/htup_details.h"
#include "access/subtrans.h"
#include "access/transam.h"
@@ -1536,8 +1537,34 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
hdr->nabortrels, abortrels,
gid);
+ /*+ * CSNSnapshot callbacks that should be called right before we are+ * going to become visible. Details in comments to this functions.+ */+ if (isCommit)+ CSNSnapshotPrecommit(proc, xid, hdr->nsubxacts, children);+ else+ CSNSnapshotAbort(proc, xid, hdr->nsubxacts, children);++
ProcArrayRemove(proc, latestXid);
+ /*+ * Stamp our transaction with CSN in CSNLog.+ * Should be called after ProcArrayEndTransaction, but before releasing+ * transaction locks, since TransactionIdGetCSN relies on+ * XactLockTableWait to await csn.+ */+ if (isCommit)+ {+ CSNSnapshotCommit(proc, xid, hdr->nsubxacts, children);+ }+ else+ {+ Assert(CSNIsInProgress(+ pg_atomic_read_u64(&proc->assignedCSN)));+ }+
/*
* In case we fail while running the callbacks, mark the gxact invalid so
* no one else will try to commit/rollback, and so it will be recycled if
@@ -2583,3 +2610,130 @@ LookupGXact(const char *gid, XLogRecPtr prepare_end_lsn,
LWLockRelease(TwoPhaseStateLock);
return found;
}
++/*+ * CSNSnapshotPrepareTwophase+ *+ * Set InDoubt state for currently active transaction and return commit's+ * global snapshot.+ */+static SnapshotCSN+CSNSnapshotPrepareTwophase(const char *gid)+{+ GlobalTransaction gxact;+ PGPROC *proc;+ char *buf;+ TransactionId xid;+ xl_xact_parsed_prepare parsed;++ if (!enable_csn_snapshot)+ ereport(ERROR,+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),+ errmsg("could not prepare transaction for global commit"),+ errhint("Make sure the configuration parameter \"%s\" is enabled.",+ "enable_csn_snapshot")));++ /*+ * Validate the GID, and lock the GXACT to ensure that two backends do not+ * try to access the same GID at once.+ */+ gxact = LockGXact(gid, GetUserId());+ proc = &ProcGlobal->allProcs[gxact->pgprocno];+ xid = proc->xid;++ if (gxact->ondisk)+ buf = ReadTwoPhaseFile(xid, true);+ else+ XlogReadTwoPhaseData(gxact->prepare_start_lsn, &buf, NULL);++ ParsePrepareRecord(0, (xl_xact_prepare *)buf, &parsed);++ CSNLogSetCSN(xid, parsed.nsubxacts,+ parsed.subxacts, InDoubtCSN, true);++ /* Unlock our GXACT */+ LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);+ gxact->locking_backend = InvalidBackendId;+ LWLockRelease(TwoPhaseStateLock);++ pfree(buf);+ return GenerateCSN(false, InvalidCSN);+}++/*+ * CSNSnapshotAssignTwoPhase+ *+ * Asign SnapshotCSN for currently active transaction. SnapshotCSN is supposedly+ * maximal among of values returned by CSNSnapshotPrepareCurrent and+ * pg_csn_snapshot_prepare.+ *+ * This function is a counterpart of CSNSnapshotAssignCurrent() for+ * twophase transactions.+ */+static void+CSNSnapshotAssignTwoPhase(const char *gid, SnapshotCSN csn)+{+ GlobalTransaction gxact;+ PGPROC *proc;++ if (!enable_csn_snapshot)+ ereport(ERROR,+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),+ errmsg("could not prepare transaction for global commit"),+ errhint("Make sure the configuration parameter \"%s\" is enabled.",+ "enable_csn_snapshot")));++ if (!CSNIsNormal(csn))+ ereport(ERROR,+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),+ errmsg("pg_csn_snapshot_assign expects normal snapshot_csn")));++ /*+ * Validate the GID, and lock the GXACT to ensure that two backends do not+ * try to access the same GID at once.+ */+ gxact = LockGXact(gid, GetUserId());+ proc = &ProcGlobal->allProcs[gxact->pgprocno];++ Assert(csn != InvalidCSN);+ /* We do not care the Generate result, we just want to make sure max+ * csnShared->last_max_csn value.+ */+ GenerateCSN(false, csn);+ /* Set snapshot_csn and defuse ProcArrayRemove from assigning one. */+ pg_atomic_write_u64(&proc->assignedCSN, csn);++ /* Unlock our GXACT */+ LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);+ gxact->locking_backend = InvalidBackendId;+ LWLockRelease(TwoPhaseStateLock);+}++/*+ * SQL interface to CSNSnapshotPrepareTwophase()+ *+ * TODO: Rewrite this as PREPARE TRANSACTION 'gid' RETURNING SNAPSHOT+ */+Datum+pg_csn_snapshot_prepare(PG_FUNCTION_ARGS)+{+ const char *gid = text_to_cstring(PG_GETARG_TEXT_PP(0));+ SnapshotCSN csn = CSNSnapshotPrepareTwophase(gid);++ PG_RETURN_INT64(csn);+}++/*+ * SQL interface to CSNSnapshotAssignTwoPhase()+ *+ * TODO: Rewrite this as COMMIT PREPARED 'gid' SNAPSHOT 'csn'+ */+Datum+pg_csn_snapshot_assign(PG_FUNCTION_ARGS)+{+ const char *gid = text_to_cstring(PG_GETARG_TEXT_PP(0));+ SnapshotCSN csn = PG_GETARG_INT64(1);++ CSNSnapshotAssignTwoPhase(gid, csn);+ PG_RETURN_VOID();+}diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.cindex a6e98e71bd..8e1d074806 100644--- a/src/backend/access/transam/varsup.c+++ b/src/backend/access/transam/varsup.c@@ -15,6 +15,7 @@
#include "access/clog.h"
#include "access/commit_ts.h"
+#include "access/csn_log.h"
#include "access/subtrans.h"
#include "access/transam.h"
#include "access/xact.h"
@@ -175,6 +176,7 @@ GetNewTransactionId(bool isSubXact)
* Extend pg_subtrans and pg_commit_ts too.
*/
ExtendCLOG(xid);
+ ExtendCSNLog(xid);
ExtendCommitTs(xid);
ExtendSUBTRANS(xid);
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.cindex 8e35c432f5..e6baf880d9 100644--- a/src/backend/access/transam/xact.c+++ b/src/backend/access/transam/xact.c@@ -21,6 +21,7 @@
#include <unistd.h>
#include "access/commit_ts.h"
+#include "access/csn_snapshot.h"
#include "access/multixact.h"
#include "access/parallel.h"
#include "access/subtrans.h"
@@ -1418,6 +1419,12 @@ RecordTransactionCommit(void)
TransactionTreeSetCommitTsData(xid, nchildren, children,
replorigin_session_origin_timestamp,
replorigin_session_origin);
++ /*+ * Mark our transaction as InDoubt in CsnLog and get ready for+ * commit.+ */+ CSNSnapshotPrecommit(MyProc, xid, nchildren, children);
}
/*
@@ -1772,6 +1779,9 @@ RecordTransactionAbort(bool isSubXact)
*/
TransactionIdAbortTree(xid, nchildren, children);
+ /* Mark our transaction as Aborted in CSN Log. */+ CSNSnapshotAbort(MyProc, xid, nchildren, children);+
END_CRIT_SECTION();
/* Compute latestXid while we have the child XIDs handy */
@@ -2114,6 +2124,13 @@ StartTransaction(void)
ShowTransactionState("StartTransaction");
}
+Datum+pg_current_csn(PG_FUNCTION_ARGS)+{+ SnapshotCSN csn = GenerateCSN(false, InvalidCSN);++ PG_RETURN_INT64(csn);+}
/*
* CommitTransaction
@@ -2262,6 +2279,21 @@ CommitTransaction(void)
*/
ProcArrayEndTransaction(MyProc, latestXid);
+ /*+ * Stamp our transaction with CSN in CsnLog.+ * Should be called after ProcArrayEndTransaction, but before releasing+ * transaction locks.+ */+ if (!is_parallel_worker)+ {+ TransactionId xid = GetTopTransactionIdIfAny();+ TransactionId *subxids;+ int nsubxids;++ nsubxids = xactGetCommittedChildren(&subxids);+ CSNSnapshotCommit(MyProc, xid, nsubxids, subxids);+ }+
/*
* This is all post-commit cleanup. Note that if an error is raised here,
* it's too late to abort the transaction. This should be just
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.cindex 1616448368..2a8de10038 100644--- a/src/backend/access/transam/xlog.c+++ b/src/backend/access/transam/xlog.c@@ -24,6 +24,7 @@
#include "access/clog.h"
#include "access/commit_ts.h"
+#include "access/csn_log.h"
#include "access/heaptoast.h"
#include "access/multixact.h"
#include "access/rewriteheap.h"
@@ -4747,6 +4748,7 @@ InitControlFile(uint64 sysidentifier)
ControlFile->wal_level = wal_level;
ControlFile->wal_log_hints = wal_log_hints;
ControlFile->track_commit_timestamp = track_commit_timestamp;
+ ControlFile->enable_csn_snapshot = enable_csn_snapshot;
ControlFile->data_checksum_version = bootstrap_data_checksum_version;
}
@@ -7181,6 +7183,9 @@ StartupXLOG(void)
if (ControlFile->track_commit_timestamp)
StartupCommitTs();
+ if(ControlFile->enable_csn_snapshot)+ StartupCSN();+
/*
* Recover knowledge about replay progress of known replication partners.
*/
@@ -7448,6 +7453,8 @@ StartupXLOG(void)
*/
StartupSUBTRANS(oldestActiveXID);
+ CSNSnapshotStartup(oldestActiveXID);+
/*
* If we're beginning at a shutdown checkpoint, we know that
* nothing was running on the primary at this point. So fake-up an
@@ -8117,7 +8124,10 @@ StartupXLOG(void)
* timestamps are started below, if necessary.)
*/
if (standbyState == STANDBY_DISABLED)
+ {
StartupSUBTRANS(oldestActiveXID);
+ CSNSnapshotStartup(oldestActiveXID);+ }
/*
* Perform end of recovery actions for any SLRUs that need it.
@@ -8183,6 +8193,7 @@ StartupXLOG(void)
* commit timestamp.
*/
CompleteCommitTsInitialization();
+ CompleteCSNInitialization();
/*
* All done with end-of-recovery actions.
@@ -9616,6 +9627,7 @@ CheckPointGuts(XLogRecPtr checkPointRedo, int flags)
TRACE_POSTGRESQL_BUFFER_CHECKPOINT_START(flags);
CheckpointStats.ckpt_write_t = GetCurrentTimestamp();
CheckPointCLOG();
+ CheckPointCSNLog();
CheckPointCommitTs();
CheckPointSUBTRANS();
CheckPointMultiXact();
@@ -9894,7 +9906,10 @@ CreateRestartPoint(int flags)
* this because StartupSUBTRANS hasn't been called yet.
*/
if (EnableHotStandby)
+ {
TruncateSUBTRANS(GetOldestTransactionIdConsideredRunning());
+ TruncateCSNLog(GetOldestTransactionIdConsideredRunning());+ }
/* Real work is done; log and update stats. */
LogCheckpointEnd(true);
@@ -10172,7 +10187,8 @@ XLogReportParameters(void)
max_wal_senders != ControlFile->max_wal_senders ||
max_prepared_xacts != ControlFile->max_prepared_xacts ||
max_locks_per_xact != ControlFile->max_locks_per_xact ||
- track_commit_timestamp != ControlFile->track_commit_timestamp)+ track_commit_timestamp != ControlFile->track_commit_timestamp ||+ enable_csn_snapshot != ControlFile->enable_csn_snapshot)
{
/*
* The change in number of backend slots doesn't need to be WAL-logged
@@ -10194,6 +10210,7 @@ XLogReportParameters(void)
xlrec.wal_level = wal_level;
xlrec.wal_log_hints = wal_log_hints;
xlrec.track_commit_timestamp = track_commit_timestamp;
+ xlrec.enable_csn_snapshot = enable_csn_snapshot;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec, sizeof(xlrec));
@@ -10212,6 +10229,7 @@ XLogReportParameters(void)
ControlFile->wal_level = wal_level;
ControlFile->wal_log_hints = wal_log_hints;
ControlFile->track_commit_timestamp = track_commit_timestamp;
+ ControlFile->enable_csn_snapshot = enable_csn_snapshot;
UpdateControlFile();
LWLockRelease(ControlFileLock);
@@ -10665,6 +10683,9 @@ xlog_redo(XLogReaderState *record)
CommitTsParameterChange(xlrec.track_commit_timestamp,
ControlFile->track_commit_timestamp);
ControlFile->track_commit_timestamp = xlrec.track_commit_timestamp;
+ CSNlogParameterChange(xlrec.enable_csn_snapshot,+ ControlFile->enable_csn_snapshot);+ ControlFile->enable_csn_snapshot = xlrec.enable_csn_snapshot;
UpdateControlFile();
LWLockRelease(ControlFileLock);
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.cindex 689384a411..e6585a94ba 100644--- a/src/backend/access/transam/xloginsert.c+++ b/src/backend/access/transam/xloginsert.c@@ -73,6 +73,8 @@ typedef struct
char compressed_page[COMPRESS_BUFSIZE];
} registered_buffer;
+bool enable_csn_wal = true;+
static registered_buffer *registered_buffers;
static int max_registered_buffers; /* allocated size */
static int max_registered_block_id = 0; /* highest block_id + 1 currently
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.cindex 5c4bc15b44..e64ada86c7 100644--- a/src/backend/commands/vacuum.c+++ b/src/backend/commands/vacuum.c@@ -53,7 +53,7 @@
#include "utils/memutils.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
-+#include "access/csn_log.h"
/*
* GUC parameters
@@ -1760,6 +1760,7 @@ vac_truncate_clog(TransactionId frozenXID,
*/
TruncateCLOG(frozenXID, oldestxid_datoid);
TruncateCommitTs(frozenXID);
+ TruncateCSNLog(frozenXID);
TruncateMultiXact(minMulti, minmulti_datoid);
/*
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.cindex dbdc172a2b..214921dc9f 100644--- a/src/backend/replication/logical/snapbuild.c+++ b/src/backend/replication/logical/snapbuild.c@@ -120,6 +120,7 @@
#include <sys/stat.h>
#include <unistd.h>
+#include "access/csn_log.h"
#include "access/heapam_xlog.h"
#include "access/transam.h"
#include "access/xact.h"
@@ -489,6 +490,9 @@ SnapBuildBuildSnapshot(SnapBuild *builder)
snapshot->xmin = builder->xmin;
snapshot->xmax = builder->xmax;
+ snapshot->snapshot_csn = FrozenCSN;+ snapshot->imported_csn = false;+
/* store all transactions to be treated as committed by this snapshot */
snapshot->xip =
(TransactionId *) ((char *) snapshot + sizeof(SnapshotData));
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.cindex 9fa3e0631e..2a7e184da9 100644--- a/src/backend/storage/ipc/ipci.c+++ b/src/backend/storage/ipc/ipci.c@@ -16,6 +16,8 @@
#include "access/clog.h"
#include "access/commit_ts.h"
+#include "access/csn_log.h"+#include "access/csn_snapshot.h"
#include "access/heapam.h"
#include "access/multixact.h"
#include "access/nbtree.h"
@@ -120,6 +122,8 @@ CalculateShmemSize(int *num_semaphores)
size = add_size(size, ProcGlobalShmemSize());
size = add_size(size, XLOGShmemSize());
size = add_size(size, CLOGShmemSize());
+ size = add_size(size, CSNLogShmemSize());+ size = add_size(size, CSNSnapshotShmemSize());
size = add_size(size, CommitTsShmemSize());
size = add_size(size, SUBTRANSShmemSize());
size = add_size(size, TwoPhaseShmemSize());
@@ -242,6 +246,8 @@ CreateSharedMemoryAndSemaphores(void)
*/
XLOGShmemInit();
CLOGShmemInit();
+ CSNLogShmemInit();+ CSNSnapshotShmemInit();
CommitTsShmemInit();
SUBTRANSShmemInit();
MultiXactShmemInit();
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.cindex 892f0f6799..5bc7370c73 100644--- a/src/backend/storage/ipc/procarray.c+++ b/src/backend/storage/ipc/procarray.c@@ -48,6 +48,7 @@
#include <signal.h>
#include "access/clog.h"
+#include "access/csn_snapshot.h"
#include "access/subtrans.h"
#include "access/transam.h"
#include "access/twophase.h"
@@ -96,6 +97,8 @@ typedef struct ProcArrayStruct
TransactionId replication_slot_xmin;
/* oldest catalog xmin of any replication slot */
TransactionId replication_slot_catalog_xmin;
+ /* xmin of oldest active csn snapshot */+ TransactionId csn_snapshot_xmin;
/* indexes into allProcs[], has PROCARRAY_MAXPROCS entries */
int pgprocnos[FLEXIBLE_ARRAY_MEMBER];
@@ -429,6 +432,7 @@ CreateSharedProcArray(void)
procArray->lastOverflowedXid = InvalidTransactionId;
procArray->replication_slot_xmin = InvalidTransactionId;
procArray->replication_slot_catalog_xmin = InvalidTransactionId;
+ procArray->csn_snapshot_xmin = InvalidTransactionId;
ShmemVariableCache->xactCompletionCount = 1;
}
@@ -577,6 +581,14 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
/* Advance global latestCompletedXid while holding the lock */
MaintainLatestCompletedXid(latestXid);
+ /*+ * Assign xid csn while holding ProcArrayLock for non-distributed+ * COMMIT PREPARED. After lock is released consequent+ * CSNSnapshotCommit() will write this value to CsnLog.+ */+ if (CSNIsInDoubt(pg_atomic_read_u64(&proc->assignedCSN)))+ pg_atomic_write_u64(&proc->assignedCSN, GenerateCSN(false, InvalidCSN));+
/* Same with xactCompletionCount */
ShmemVariableCache->xactCompletionCount++;
@@ -691,6 +703,7 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
proc->xmin = InvalidTransactionId;
proc->delayChkpt = false; /* be sure this is cleared in abort */
proc->recoveryConflictPending = false;
+ proc->originalXmin = InvalidTransactionId;
/* must be cleared with xid/xmin: */
/* avoid unnecessarily dirtying shared cachelines */
@@ -730,6 +743,7 @@ ProcArrayEndTransactionInternal(PGPROC *proc, TransactionId latestXid)
proc->xmin = InvalidTransactionId;
proc->delayChkpt = false; /* be sure this is cleared in abort */
proc->recoveryConflictPending = false;
+ proc->originalXmin = InvalidTransactionId;
/* must be cleared with xid/xmin: */
/* avoid unnecessarily dirtying shared cachelines */
@@ -753,6 +767,16 @@ ProcArrayEndTransactionInternal(PGPROC *proc, TransactionId latestXid)
/* Also advance global latestCompletedXid while holding the lock */
MaintainLatestCompletedXid(latestXid);
+ /*+ * Assign xid csn while holding ProcArrayLock for+ * COMMIT.+ *+ * TODO: in case of group commit we can generate one CSNSnapshot for+ * whole group to save time on timestamp aquisition.+ */+ if (CSNIsInDoubt(pg_atomic_read_u64(&proc->assignedCSN)))+ pg_atomic_write_u64(&proc->assignedCSN, GenerateCSN(false, InvalidCSN));+
/* Same with xactCompletionCount */
ShmemVariableCache->xactCompletionCount++;
}
@@ -912,6 +936,7 @@ ProcArrayClearTransaction(PGPROC *proc)
proc->lxid = InvalidLocalTransactionId;
proc->xmin = InvalidTransactionId;
proc->recoveryConflictPending = false;
+ proc->originalXmin = InvalidTransactionId;
Assert(!(proc->statusFlags & PROC_VACUUM_STATE_MASK));
Assert(!proc->delayChkpt);
@@ -1204,6 +1229,7 @@ ProcArrayApplyRecoveryInfo(RunningTransactions running)
while (TransactionIdPrecedes(latestObservedXid, running->nextXid))
{
ExtendSUBTRANS(latestObservedXid);
+ ExtendCSNLog(latestObservedXid);
TransactionIdAdvance(latestObservedXid);
}
TransactionIdRetreat(latestObservedXid); /* = running->nextXid - 1 */
@@ -1704,6 +1730,7 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h)
TransactionId kaxmin;
bool in_recovery = RecoveryInProgress();
TransactionId *other_xids = ProcGlobal->xids;
+ TransactionId csn_snapshot_xmin = InvalidTransactionId;
LWLockAcquire(ProcArrayLock, LW_SHARED);
@@ -1843,6 +1870,10 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h)
if (in_recovery)
kaxmin = KnownAssignedXidsGetOldestXmin();
+ /* Get value of xmin, delayed by a CSN snapshot settings. */+ if (get_csnlog_status() && csn_snapshot_defer_time > 0 && IsUnderPostmaster)+ csn_snapshot_xmin = ProcArrayGetCSNSnapshotXmin();+
/*
* No other information from shared state is needed, release the lock
* immediately. The rest of the computations can be done without a lock.
@@ -1899,6 +1930,15 @@ ComputeXidHorizons(ComputeXidHorizonsResult *h)
h->data_oldest_nonremovable =
TransactionIdOlder(h->data_oldest_nonremovable, h->slot_xmin);
+ /*+ * Hold non-removable border because distributed transactions+ * can wish to see old data.+ */+ h->shared_oldest_nonremovable =+ TransactionIdOlder(h->shared_oldest_nonremovable, csn_snapshot_xmin);+ h->data_oldest_nonremovable =+ TransactionIdOlder(h->data_oldest_nonremovable, csn_snapshot_xmin);+
/*
* The only difference between catalog / data horizons is that the slot's
* catalog xmin is applied to the catalog one (so catalogs can be accessed
@@ -2133,6 +2173,9 @@ GetSnapshotDataReuse(Snapshot snapshot)
if (curXactCompletionCount != snapshot->snapXactCompletionCount)
return false;
+ if (get_csnlog_status())+ return false;+
/*
* If the current xactCompletionCount is still the same as it was at the
* time the snapshot was built, we can be sure that rebuilding the
@@ -2212,6 +2255,8 @@ GetSnapshotData(Snapshot snapshot)
int count = 0;
int subcount = 0;
bool suboverflowed = false;
+ CSN csn = FrozenCSN;+ TransactionId csn_snapshot_xmin = InvalidTransactionId;
FullTransactionId latest_completed;
TransactionId oldestxid;
int mypgxactoff;
@@ -2444,6 +2489,20 @@ GetSnapshotData(Snapshot snapshot)
if (!TransactionIdIsValid(MyProc->xmin))
MyProc->xmin = TransactionXmin = xmin;
+ /* Take CSN under ProcArrayLock so the snapshot stays synchronized. */+ if (!snapshot->takenDuringRecovery && get_csnlog_status())+ csn = GenerateCSN(false, InvalidCSN);++ if (get_csnlog_status() && csn_snapshot_defer_time > 0 && IsUnderPostmaster)+ {+ CSNSnapshotMapXmin(snapshot->snapshot_csn);++ /* Get value of xmin, delayed by a CSN snapshot settings. */+ csn_snapshot_xmin = ProcArrayGetCSNSnapshotXmin();+ /* Adjust an oldest xid value with a xmin, delayed by CSN options. */+ oldestxid = TransactionIdOlder(oldestxid, csn_snapshot_xmin);+ }+
LWLockRelease(ProcArrayLock);
/* maintain state for GlobalVis* */
@@ -2469,6 +2528,10 @@ GetSnapshotData(Snapshot snapshot)
def_vis_xid_data =
TransactionIdOlder(def_vis_xid_data, replication_slot_xmin);
+ /* The csn-related settings can require an older xmin. */+ def_vis_xid_data =+ TransactionIdOlder(def_vis_xid_data, csn_snapshot_xmin);+
/*
* Rows in non-shared, non-catalog tables possibly could be vacuumed
* if older than this xid.
@@ -2549,6 +2612,8 @@ GetSnapshotData(Snapshot snapshot)
snapshot->active_count = 0;
snapshot->regd_count = 0;
snapshot->copied = false;
+ snapshot->imported_csn = false;+ snapshot->snapshot_csn = csn;
GetSnapshotDataInitOldSnapshot(snapshot);
@@ -3901,6 +3966,25 @@ ProcArrayGetReplicationSlotXmin(TransactionId *xmin,
LWLockRelease(ProcArrayLock);
}
+/*+ * ProcArraySetCSNSnapshotXmin+ */+void+ProcArraySetCSNSnapshotXmin(TransactionId xmin)+{+ /* We rely on atomic fetch/store of xid */+ procArray->csn_snapshot_xmin = xmin;+}++/*+ * ProcArrayGetCSNSnapshotXmin+ */+TransactionId+ProcArrayGetCSNSnapshotXmin(void)+{+ return procArray->csn_snapshot_xmin;+}+
/*
* XidCacheRemoveRunningXids
*
@@ -4383,6 +4467,7 @@ RecordKnownAssignedTransactionIds(TransactionId xid)
while (TransactionIdPrecedes(next_expected_xid, xid))
{
TransactionIdAdvance(next_expected_xid);
+ ExtendCSNLog(next_expected_xid);
ExtendSUBTRANS(next_expected_xid);
}
Assert(next_expected_xid == xid);
diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.cindex 862097352b..1f78161d9a 100644--- a/src/backend/storage/lmgr/lwlock.c+++ b/src/backend/storage/lmgr/lwlock.c@@ -135,6 +135,8 @@ static const char *const BuiltinTrancheNames[] = {
"CommitTSBuffer",
/* LWTRANCHE_SUBTRANS_BUFFER: */
"SubtransBuffer",
+ /* LWTRANCHE_CSN_LOG_BUFFERS */+ "CSNLogBuffer",
/* LWTRANCHE_MULTIXACTOFFSET_BUFFER: */
"MultiXactOffsetBuffer",
/* LWTRANCHE_MULTIXACTMEMBER_BUFFER: */
diff --git a/src/backend/storage/lmgr/lwlocknames.txt b/src/backend/storage/lmgr/lwlocknames.txtindex 6c7cf6c295..e8ca393611 100644--- a/src/backend/storage/lmgr/lwlocknames.txt+++ b/src/backend/storage/lmgr/lwlocknames.txt@@ -53,3 +53,5 @@ XactTruncationLock 44
# 45 was XactTruncationLock until removal of BackendRandomLock
WrapLimitsVacuumLock 46
NotifyQueueTailLock 47
+CSNLogSLRULock 48+CSNSnapshotXidMapLock 49diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.cindex b7d9da0aa9..88f4f42456 100644--- a/src/backend/storage/lmgr/proc.c+++ b/src/backend/storage/lmgr/proc.c@@ -35,9 +35,11 @@
#include <unistd.h>
#include <sys/time.h>
+#include "access/csn_snapshot.h"
#include "access/transam.h"
#include "access/twophase.h"
#include "access/xlogutils.h"
+#include "access/xact.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
@@ -440,6 +442,9 @@ InitProcess(void)
MyProc->clogGroupMemberLsn = InvalidXLogRecPtr;
Assert(pg_atomic_read_u32(&MyProc->clogGroupNext) == INVALID_PGPROCNO);
+ MyProc->originalXmin = InvalidTransactionId;+ pg_atomic_init_u64(&MyProc->assignedCSN, InProgressCSN);+
/*
* Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
* on it. That allows us to repoint the process latch, which so far
@@ -585,6 +590,7 @@ InitAuxiliaryProcess(void)
MyProc->lwWaitMode = 0;
MyProc->waitLock = NULL;
MyProc->waitProcLock = NULL;
+ MyProc->originalXmin = InvalidTransactionId;
pg_atomic_write_u64(&MyProc->waitStart, 0);
#ifdef USE_ASSERT_CHECKING
{
diff --git a/src/backend/storage/sync/sync.c b/src/backend/storage/sync/sync.cindex d4083e8a56..383f1e4566 100644--- a/src/backend/storage/sync/sync.c+++ b/src/backend/storage/sync/sync.c@@ -20,6 +20,7 @@
#include "access/commit_ts.h"
#include "access/clog.h"
+#include "access/csn_log.h"
#include "access/multixact.h"
#include "access/xlog.h"
#include "access/xlogutils.h"
@@ -119,6 +120,10 @@ static const SyncOps syncsw[] = {
/* pg_multixact/members */
[SYNC_HANDLER_MULTIXACT_MEMBER] = {
.sync_syncfiletag = multixactmemberssyncfiletag
+ },+ /* pg_multixact/members */+ [SYNC_HANDLER_CSN] = {+ .sync_syncfiletag = csnsyncfiletag
}
};
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.cindex e91d5a3cfd..4d9833fb5f 100644--- a/src/backend/utils/misc/guc.c+++ b/src/backend/utils/misc/guc.c@@ -34,6 +34,7 @@
#include "access/commit_ts.h"
#include "access/gin.h"
+#include "access/csn_snapshot.h"
#include "access/rmgr.h"
#include "access/tableam.h"
#include "access/toast_compression.h"
@@ -1212,6 +1213,24 @@ static struct config_bool ConfigureNamesBool[] =
false,
NULL, NULL, NULL
},
+ {+ {"enable_csn_snapshot", PGC_POSTMASTER, RESOURCES_MEM,+ gettext_noop("Enable csn-base snapshot."),+ gettext_noop("Used to achieve REPEATABLE READ isolation level for postgres_fdw transactions.")+ },+ &enable_csn_snapshot,+ true,+ NULL, NULL, NULL+ },+ {+ {"enable_csn_wal", PGC_POSTMASTER, RESOURCES_MEM,+ gettext_noop("Enable csn-wal record."),+ gettext_noop("Used to enable csn-wal record")+ },+ &enable_csn_wal,+ true,+ NULL, NULL, NULL+ },
{
{"ssl", PGC_SIGHUP, CONN_AUTH_SSL,
gettext_noop("Enables SSL connections."),
@@ -3195,6 +3214,24 @@ static struct config_int ConfigureNamesInt[] =
NULL, NULL, NULL
},
+ {+ {"csn_snapshot_defer_time", PGC_POSTMASTER, REPLICATION_PRIMARY,+ gettext_noop("Minimal age of records which allowed to be vacuumed, in seconds."),+ NULL+ },+ &csn_snapshot_defer_time,+ 0, 0, INT_MAX,+ NULL, NULL, NULL+ },+ {+ {"csn_time_shift", PGC_USERSET, RESOURCES_MEM,+ gettext_noop("Do the time shift in the CSN generator."),+ gettext_noop("Used for debug purposes.")+ },+ &csn_time_shift,+ 0, INT_MIN, INT_MAX,+ NULL, NULL, NULL+ },
{
{"block_size", PGC_INTERNAL, PRESET_OPTIONS,
gettext_noop("Shows the size of a disk block."),
diff --git a/src/backend/utils/probes.d b/src/backend/utils/probes.dindex b0c50a3c7f..3fcd0f4ccf 100644--- a/src/backend/utils/probes.d+++ b/src/backend/utils/probes.d@@ -77,6 +77,8 @@ provider postgresql {
probe clog__checkpoint__done(bool);
probe subtrans__checkpoint__start(bool);
probe subtrans__checkpoint__done(bool);
+ probe csnlog__checkpoint__start(bool);+ probe csnlog__checkpoint__done(bool);
probe multixact__checkpoint__start(bool);
probe multixact__checkpoint__done(bool);
probe twophase__checkpoint__start();
diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.cindex 5001efdf7a..5a52fce2ed 100644--- a/src/backend/utils/time/snapmgr.c+++ b/src/backend/utils/time/snapmgr.c@@ -48,6 +48,7 @@
#include <sys/stat.h>
#include <unistd.h>
+#include "access/csn_log.h"
#include "access/subtrans.h"
#include "access/transam.h"
#include "access/xact.h"
@@ -77,6 +78,8 @@
*/
int old_snapshot_threshold; /* number of minutes, -1 disables */
+bool enable_csn_snapshot;+
volatile OldSnapshotControlData *oldSnapshotControl;
@@ -173,6 +176,7 @@ static TimestampTz AlignTimestampToMinuteBoundary(TimestampTz ts);
static Snapshot CopySnapshot(Snapshot snapshot);
static void FreeSnapshot(Snapshot snapshot);
static void SnapshotResetXmin(void);
+static bool XidInLocalMVCCSnapshot(TransactionId xid, Snapshot snapshot);
/*
* Snapshot fields to be serialized.
@@ -191,6 +195,8 @@ typedef struct SerializedSnapshotData
CommandId curcid;
TimestampTz whenTaken;
XLogRecPtr lsn;
+ CSN csn;+ bool imported_csn;
} SerializedSnapshotData;
Size
@@ -544,6 +550,8 @@ SetTransactionSnapshot(Snapshot sourcesnap, VirtualTransactionId *sourcevxid,
sourcesnap->subxcnt * sizeof(TransactionId));
CurrentSnapshot->suboverflowed = sourcesnap->suboverflowed;
CurrentSnapshot->takenDuringRecovery = sourcesnap->takenDuringRecovery;
+ CurrentSnapshot->snapshot_csn = sourcesnap->snapshot_csn;+ CurrentSnapshot->imported_csn = sourcesnap->imported_csn;
/* NB: curcid should NOT be copied, it's a local matter */
CurrentSnapshot->snapXactCompletionCount = 0;
@@ -1209,6 +1217,10 @@ ExportSnapshot(Snapshot snapshot)
appendStringInfo(&buf, "xmin:%u\n", snapshot->xmin);
appendStringInfo(&buf, "xmax:%u\n", snapshot->xmax);
+ appendStringInfo(&buf, "snapshot_csn:"UINT64_FORMAT"\n",+ snapshot->snapshot_csn);+ appendStringInfo(&buf, "imported_csn:%u\n", snapshot->imported_csn);+
/*
* We must include our own top transaction ID in the top-xid data, since
* by definition we will still be running when the importing transaction
@@ -1333,6 +1345,31 @@ parseIntFromText(const char *prefix, char **s, const char *filename)
return val;
}
+static CSN+parseCSNFromText(const char *prefix, char **s, const char *filename)+{+ char *ptr = *s;+ int prefixlen = strlen(prefix);+ uint64 val;++ if (strncmp(ptr, prefix, prefixlen) != 0)+ ereport(ERROR,+ (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),+ errmsg("invalid snapshot data in file \"%s\"", filename)));+ ptr += prefixlen;+ if (sscanf(ptr, UINT64_FORMAT, &val) != 1)+ ereport(ERROR,+ (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),+ errmsg("invalid snapshot data in file \"%s\"", filename)));+ ptr = strchr(ptr, '\n');+ if (!ptr)+ ereport(ERROR,+ (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),+ errmsg("invalid snapshot data in file \"%s\"", filename)));+ *s = ptr + 1;+ return val;+}+
static TransactionId
parseXidFromText(const char *prefix, char **s, const char *filename)
{
@@ -1474,6 +1511,9 @@ ImportSnapshot(const char *idstr)
snapshot.xmin = parseXidFromText("xmin:", &filebuf, path);
snapshot.xmax = parseXidFromText("xmax:", &filebuf, path);
+ snapshot.snapshot_csn = parseCSNFromText("snapshot_csn:", &filebuf, path);+ snapshot.imported_csn = parseIntFromText("imported_csn:", &filebuf, path);+
snapshot.xcnt = xcnt = parseIntFromText("xcnt:", &filebuf, path);
/* sanity-check the xid count before palloc */
@@ -2130,6 +2170,8 @@ SerializeSnapshot(Snapshot snapshot, char *start_address)
serialized_snapshot.curcid = snapshot->curcid;
serialized_snapshot.whenTaken = snapshot->whenTaken;
serialized_snapshot.lsn = snapshot->lsn;
+ serialized_snapshot.csn = snapshot->snapshot_csn;+ serialized_snapshot.imported_csn = snapshot->imported_csn;
/*
* Ignore the SubXID array if it has overflowed, unless the snapshot was
@@ -2204,6 +2246,8 @@ RestoreSnapshot(char *start_address)
snapshot->curcid = serialized_snapshot.curcid;
snapshot->whenTaken = serialized_snapshot.whenTaken;
snapshot->lsn = serialized_snapshot.lsn;
+ snapshot->snapshot_csn = serialized_snapshot.csn;+ snapshot->imported_csn = serialized_snapshot.imported_csn;
snapshot->snapXactCompletionCount = 0;
/* Copy XIDs, if present. */
@@ -2245,6 +2289,44 @@ RestoreTransactionSnapshot(Snapshot snapshot, void *source_pgproc)
/*
* XidInMVCCSnapshot
+ *+ * Check whether this xid is in snapshot. When enable_csn_snapshot is+ * switched off just call XidInLocalMVCCSnapshot().+ */+bool+XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)+{+ bool in_snapshot;++ if (snapshot->imported_csn)+ {+ Assert(enable_csn_snapshot);+ /* No point to using snapshot info except CSN */+ return XidInCSNSnapshot(xid, snapshot);+ }++ in_snapshot = XidInLocalMVCCSnapshot(xid, snapshot);++ if (!get_csnlog_status())+ {+ Assert(CSNIsFrozen(snapshot->snapshot_csn));+ return in_snapshot;+ }++ if (in_snapshot)+ {+ /*+ * This xid may be already in unknown state and in that case+ * we must wait and recheck.+ */+ return XidInCSNSnapshot(xid, snapshot);+ }+ else+ return false;+}++/*+ * XidInLocalMVCCSnapshot
* Is the given XID still-in-progress according to the snapshot?
*
* Note: GetSnapshotData never stores either top xid or subxids of our own
@@ -2253,8 +2335,8 @@ RestoreTransactionSnapshot(Snapshot snapshot, void *source_pgproc)
* TransactionIdIsCurrentTransactionId first, except when it's known the
* XID could not be ours anyway.
*/
-bool-XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)+static bool+XidInLocalMVCCSnapshot(TransactionId xid, Snapshot snapshot)
{
uint32 i;
@@ -2364,3 +2446,100 @@ XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
return false;
}
+++/*+ * ExportCSNSnapshot+ *+ * Export snapshot_csn so that caller can expand this transaction to other+ * nodes.+ *+ * TODO: it's better to do this through EXPORT/IMPORT SNAPSHOT syntax and+ * add some additional checks that transaction did not yet acquired xid, but+ * for current iteration of this patch I don't want to hack on parser.+ */+SnapshotCSN+ExportCSNSnapshot()+{+ if (!get_csnlog_status())+ ereport(ERROR,+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),+ errmsg("could not export csn snapshot"),+ errhint("Make sure the configuration parameter \"%s\" is enabled.",+ "enable_csn_snapshot")));++ elog(DEBUG5, "Export CSN Snapshot: csn = %lu",+ CurrentSnapshot->snapshot_csn);+ return CurrentSnapshot->snapshot_csn;+}++/* SQL accessor to ExportCSNSnapshot() */+Datum+pg_csn_snapshot_export(PG_FUNCTION_ARGS)+{+ SnapshotCSN csn = ExportCSNSnapshot();++ PG_RETURN_UINT64(csn);+}++/*+ * ImportCSNSnapshot+ *+ * Import csn and retract this backends xmin to the value that was+ * actual when we had such csn.+ *+ * TODO: it's better to do this through EXPORT/IMPORT SNAPSHOT syntax and+ * add some additional checks that transaction did not yet acquired xid, but+ * for current iteration of this patch I don't want to hack on parser.+ */+void+ImportCSNSnapshot(SnapshotCSN snapshot_csn)+{+ volatile TransactionId xmin;++ if (!get_csnlog_status())+ ereport(ERROR,+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),+ errmsg("could not import csn snapshot"),+ errhint("Make sure the configuration parameter \"%s\" is enabled.",+ "enable_csn_snapshot")));++ if (csn_snapshot_defer_time <= 0)+ ereport(ERROR,+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),+ errmsg("could not import csn snapshot"),+ errhint("Make sure the configuration parameter \"%s\" is positive.",+ "csn_snapshot_defer_time")));++ /*+ * Call CSNSnapshotToXmin under ProcArrayLock to avoid situation that+ * resulting xmin will be evicted from map before we will set it into our+ * backend's xmin.+ */+ LWLockAcquire(ProcArrayLock, LW_SHARED);+ xmin = CSNSnapshotToXmin(snapshot_csn);+ if (!TransactionIdIsValid(xmin))+ {+ LWLockRelease(ProcArrayLock);+ elog(ERROR, "CSNSnapshotToXmin: csn snapshot too old");+ }++ MyProc->originalXmin = MyProc->xmin;+ MyProc->xmin = TransactionXmin = xmin;+ LWLockRelease(ProcArrayLock);++ CurrentSnapshot->xmin = xmin; /* defuse SnapshotResetXmin() */+ CurrentSnapshot->snapshot_csn = snapshot_csn;+ CurrentSnapshot->imported_csn = true;+ CSNSnapshotSync(snapshot_csn);+}++/* SQL accessor to ImportCSNSnapshot() */+Datum+pg_csn_snapshot_import(PG_FUNCTION_ARGS)+{+ SnapshotCSN csn = PG_GETARG_UINT64(0);++ ImportCSNSnapshot(csn);+ PG_RETURN_VOID();+}diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.cindex 31839c1a19..1864952bd2 100644--- a/src/bin/initdb/initdb.c+++ b/src/bin/initdb/initdb.c@@ -227,7 +227,8 @@ static const char *const subdirs[] = {
"pg_xact",
"pg_logical",
"pg_logical/snapshots",
- "pg_logical/mappings"+ "pg_logical/mappings",+ "pg_csn"
};
diff --git a/src/bin/pg_controldata/pg_controldata.c b/src/bin/pg_controldata/pg_controldata.cindex f911f98d94..325e6a0e2b 100644--- a/src/bin/pg_controldata/pg_controldata.c+++ b/src/bin/pg_controldata/pg_controldata.c@@ -300,6 +300,8 @@ main(int argc, char *argv[])
ControlFile->max_locks_per_xact);
printf(_("track_commit_timestamp setting: %s\n"),
ControlFile->track_commit_timestamp ? _("on") : _("off"));
+ printf(_("enable_csn_snapshot setting: %s\n"),+ ControlFile->enable_csn_snapshot ? _("on") : _("off"));
printf(_("Maximum data alignment: %u\n"),
ControlFile->maxAlign);
/* we don't print floatFormat since can't say much useful about it */
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.cindex 3628bd74a7..18cf9197cc 100644--- a/src/bin/pg_upgrade/pg_upgrade.c+++ b/src/bin/pg_upgrade/pg_upgrade.c@@ -548,6 +548,11 @@ copy_xact_xlog_xid(void)
check_ok();
}
+ if(old_cluster.controldata.cat_ver > CSN_BASE_SNAPSHOT_ADD_VER)+ {+ copy_subdir_files("pg_csn", "pg_csn");+ }+
/* now reset the wal archives in the new cluster */
prep_status("Resetting WAL archives");
exec_prog(UTILITY_LOG_FILE, NULL, true, true,
diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.hindex ca0795f68f..54f2984387 100644--- a/src/bin/pg_upgrade/pg_upgrade.h+++ b/src/bin/pg_upgrade/pg_upgrade.h@@ -124,6 +124,8 @@ extern char *output_files[];
*/
#define JSONB_FORMAT_CHANGE_CAT_VER 201409291
+#define CSN_BASE_SNAPSHOT_ADD_VER 202002010+
/*
* Each relation is represented by a relinfo structure.
diff --git a/src/bin/pg_waldump/rmgrdesc.c b/src/bin/pg_waldump/rmgrdesc.cindex 852d8ca4b1..2d280ce940 100644--- a/src/bin/pg_waldump/rmgrdesc.c+++ b/src/bin/pg_waldump/rmgrdesc.c@@ -11,6 +11,7 @@
#include "access/brin_xlog.h"
#include "access/clog.h"
#include "access/commit_ts.h"
+#include "access/csn_log.h"
#include "access/generic_xlog.h"
#include "access/ginxlog.h"
#include "access/gistxlog.h"
diff --git a/src/include/access/csn_log.h b/src/include/access/csn_log.hnew file mode 100644index 0000000000..12df028bf4--- /dev/null+++ b/src/include/access/csn_log.h@@ -0,0 +1,98 @@+/*+ * csn_log.h+ *+ * Commit-Sequence-Number log.+ *+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group+ * Portions Copyright (c) 1994, Regents of the University of California+ *+ * src/include/access/csn_log.h+ */+#ifndef CSNLOG_H+#define CSNLOG_H++#include "access/xlog.h"+#include "utils/snapshot.h"+#include "storage/sync.h"+++#define InProgressCSN UINT64CONST(0x0)+#define AbortedCSN UINT64CONST(0x1)+#define FrozenCSN UINT64CONST(0x2)+#define InDoubtCSN UINT64CONST(0x3)+#define UnclearCSN UINT64CONST(0x4)+#define FirstNormalCSN UINT64CONST(0x5)++#define CSNIsInProgress(csn) ((csn) == InProgressCSN)+#define CSNIsAborted(csn) ((csn) == AbortedCSN)+#define CSNIsFrozen(csn) ((csn) == FrozenCSN)+#define CSNIsInDoubt(csn) ((csn) == InDoubtCSN)+#define CSNIsUnclear(csn) ((csn) == UnclearCSN)+#define CSNIsNormal(csn) ((csn) >= FirstNormalCSN)++/* XLOG stuff */+#define XLOG_CSN_ASSIGNMENT 0x00+#define XLOG_CSN_SETCSN 0x10+#define XLOG_CSN_ZEROPAGE 0x20+#define XLOG_CSN_TRUNCATE 0x30++/*+ * We should log MAX generated CSN to wal, so that database will not generate+ * a historical CSN after database restart. This may appear when system time+ * turned back.+ *+ * However we can not log the MAX CSN every time it generated, if so it will+ * cause too many wal expend, so we log it 5s more in the future.+ *+ * As a trade off, when this database restart, there will be 5s bad performance+ * for time synchronization among sharding nodes.+ *+ * It looks like we can redefine this as a configure parameter, and the user+ * can decide which way they prefer.+ *+ */+#define CSN_ASSIGN_TIME_INTERVAL 5++typedef struct xl_csn_set+{+ CSN csn;+ TransactionId xtop; /* XID's top-level XID */+ int nsubxacts; /* number of subtransaction XIDs */+ TransactionId xsub[FLEXIBLE_ARRAY_MEMBER]; /* assigned subxids */+} xl_csn_set;++#define MinSizeOfCSNSet offsetof(xl_csn_set, xsub)+#define CSNAddByNanosec(csn,second) (csn + second * 1000000000L)++/* Main functions */+extern void CSNLogSetCSN(TransactionId xid, int nsubxids,+ TransactionId *subxids, CSN csn, bool write_xlog);+extern CSN CSNLogGetCSNByXid(TransactionId xid);++/* Infrastructure functions */+extern Size CSNLogShmemSize(void);+extern void CSNLogShmemInit(void);+extern void ActivateCSNlog(void);+extern void ExtendCSNLog(TransactionId newestXact);+extern void DeactivateCSNlog(void);++extern void CheckPointCSNLog(void);+extern void TruncateCSNLog(TransactionId oldestXact);++extern void csnlog_redo(XLogReaderState *record);+extern void csnlog_desc(StringInfo buf, XLogReaderState *record);+extern const char *csnlog_identify(uint8 info);+extern void WriteAssignCSNXlogRec(CSN csn);+extern void CatchCSNLog(void);+extern void StartupCSN(void);+extern void CompleteCSNInitialization(void);+extern void CSNlogParameterChange(bool newvalue, bool oldvalue);+extern bool get_csnlog_status(void);+extern int csnsyncfiletag(const FileTag *ftag, char *path);++extern CSN GenerateCSN(bool locked, CSN assign);+extern CSN GetLastGeneratedCSN(void);++extern TransactionId GetOldestXmin(void);++#endif /* CSNLOG_H */
\ No newline at end of file
diff --git a/src/include/access/csn_snapshot.h b/src/include/access/csn_snapshot.hnew file mode 100644index 0000000000..916603af0c--- /dev/null+++ b/src/include/access/csn_snapshot.h@@ -0,0 +1,54 @@+/*-------------------------------------------------------------------------+ *+ * csn_snapshot.h+ * Support for cross-node snapshot isolation.+ *+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group+ * Portions Copyright (c) 1994, Regents of the University of California+ *+ * src/include/access/csn_snapshot.h+ *+ *-------------------------------------------------------------------------+ */+#ifndef CSN_SNAPSHOT_H+#define CSN_SNAPSHOT_H++#include "access/csn_log.h"+#include "port/atomics.h"+#include "storage/lock.h"+#include "utils/snapshot.h"+#include "utils/guc.h"++/*+ * snapshot.h is used in frontend code so atomic variant of SnapshotCSN type+ * is defined here.+ */+typedef pg_atomic_uint64 CSN_atomic;+++extern int csn_snapshot_defer_time;+extern int csn_time_shift;+++extern Size CSNSnapshotShmemSize(void);+extern void CSNSnapshotShmemInit(void);+extern void CSNSnapshotStartup(TransactionId oldestActiveXID);++extern void CSNSnapshotMapXmin(SnapshotCSN snapshot_csn);+extern TransactionId CSNSnapshotToXmin(SnapshotCSN snapshot_csn);++extern bool XidInCSNSnapshot(TransactionId xid, Snapshot snapshot);++extern CSN TransactionIdGetCSN(TransactionId xid);++extern void CSNSnapshotAbort(PGPROC *proc, TransactionId xid, int nsubxids,+ TransactionId *subxids);+extern void CSNSnapshotPrecommit(PGPROC *proc, TransactionId xid, int nsubxids,+ TransactionId *subxids);+extern void CSNSnapshotCommit(PGPROC *proc, TransactionId xid, int nsubxids,+ TransactionId *subxids);+extern void CSNSnapshotAssignCurrent(SnapshotCSN snapshot_csn);+extern SnapshotCSN CSNSnapshotPrepareCurrent(void);+extern void CSNSnapshotSync(SnapshotCSN remote_csn);++#endif /* CSN_SNAPSHOT_H */diff --git a/src/include/access/rmgrlist.h b/src/include/access/rmgrlist.hindex f582cf535f..3cf0775176 100644--- a/src/include/access/rmgrlist.h+++ b/src/include/access/rmgrlist.h@@ -47,3 +47,4 @@ PG_RMGR(RM_COMMIT_TS_ID, "CommitTs", commit_ts_redo, commit_ts_desc, commit_ts_i
PG_RMGR(RM_REPLORIGIN_ID, "ReplicationOrigin", replorigin_redo, replorigin_desc, replorigin_identify, NULL, NULL, NULL)
PG_RMGR(RM_GENERIC_ID, "Generic", generic_redo, generic_desc, generic_identify, NULL, NULL, generic_mask)
PG_RMGR(RM_LOGICALMSG_ID, "LogicalMessage", logicalmsg_redo, logicalmsg_desc, logicalmsg_identify, NULL, NULL, NULL)
+PG_RMGR(RM_CSNLOG_ID, "CSN", csnlog_redo, csnlog_desc, csnlog_identify, NULL, NULL, NULL)diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.hindex c0da76cab4..2ee489dcad 100644--- a/src/include/access/xlog_internal.h+++ b/src/include/access/xlog_internal.h@@ -242,6 +242,7 @@ typedef struct xl_parameter_change
int wal_level;
bool wal_log_hints;
bool track_commit_timestamp;
+ bool enable_csn_snapshot;
} xl_parameter_change;
/* logs restore point */
@@ -332,5 +333,6 @@ extern bool ArchiveRecoveryRequested;
extern bool InArchiveRecovery;
extern bool StandbyMode;
extern char *recoveryRestoreCommand;
+extern bool enable_csn_wal;
#endif /* XLOG_INTERNAL_H */
diff --git a/src/include/catalog/pg_control.h b/src/include/catalog/pg_control.hindex 749bce0cc6..a7da532f3a 100644--- a/src/include/catalog/pg_control.h+++ b/src/include/catalog/pg_control.h@@ -183,6 +183,7 @@ typedef struct ControlFileData
int max_prepared_xacts;
int max_locks_per_xact;
bool track_commit_timestamp;
+ bool enable_csn_snapshot;
/*
* This data is used to check for hardware-architecture compatibility of
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.datindex d068d6532e..d578aceb40 100644--- a/src/include/catalog/pg_proc.dat+++ b/src/include/catalog/pg_proc.dat@@ -11689,4 +11689,21 @@
prorettype => 'bytea', proargtypes => 'pg_brin_minmax_multi_summary',
prosrc => 'brin_minmax_multi_summary_send' },
+# csn shnapshot handling+{ oid => '10001', descr => 'export csn snapshot',+ proname => 'pg_csn_snapshot_export', provolatile => 'v', proparallel => 'u',+ prorettype => 'int8', proargtypes => '', prosrc => 'pg_csn_snapshot_export' },+{ oid => '10002', descr => 'import csn snapshot',+ proname => 'pg_csn_snapshot_import', provolatile => 'v', proparallel => 'u',+ prorettype => 'void', proargtypes => 'int8', prosrc => 'pg_csn_snapshot_import' },+{ oid => '10003', descr => 'prepare distributed transaction for commit, get csn',+ proname => 'pg_csn_snapshot_prepare', provolatile => 'v', proparallel => 'u',+ prorettype => 'int8', proargtypes => 'text', prosrc => 'pg_csn_snapshot_prepare' },+{ oid => '10004', descr => 'assign csn to distributed transaction',+ proname => 'pg_csn_snapshot_assign', provolatile => 'v', proparallel => 'u',+ prorettype => 'void', proargtypes => 'text int8', prosrc => 'pg_csn_snapshot_assign' },+{ oid => '10005', descr => 'get current CSN',+ proname => 'pg_current_csn', provolatile => 'v', proparallel => 'u',+ prorettype => 'int8', proargtypes => '', prosrc => 'pg_current_csn' },+
]
diff --git a/src/include/datatype/timestamp.h b/src/include/datatype/timestamp.hindex 99873497a6..8d1ced7430 100644--- a/src/include/datatype/timestamp.h+++ b/src/include/datatype/timestamp.h@@ -93,6 +93,9 @@ typedef struct
#define USECS_PER_MINUTE INT64CONST(60000000)
#define USECS_PER_SEC INT64CONST(1000000)
+#define NSECS_PER_SEC INT64CONST(1000000000)+#define NSECS_PER_USEC INT64CONST(1000)+
/*
* We allow numeric timezone offsets up to 15:59:59 either way from Greenwich.
* Currently, the record holders for wackiest offsets in actual use are zones
diff --git a/src/include/fmgr.h b/src/include/fmgr.hindex ab7b85c86e..f08999740b 100644--- a/src/include/fmgr.h+++ b/src/include/fmgr.h@@ -281,6 +281,7 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena *datum);
#define PG_GETARG_FLOAT4(n) DatumGetFloat4(PG_GETARG_DATUM(n))
#define PG_GETARG_FLOAT8(n) DatumGetFloat8(PG_GETARG_DATUM(n))
#define PG_GETARG_INT64(n) DatumGetInt64(PG_GETARG_DATUM(n))
+#define PG_GETARG_UINT64(n) DatumGetUInt64(PG_GETARG_DATUM(n))
/* use this if you want the raw, possibly-toasted input datum: */
#define PG_GETARG_RAW_VARLENA_P(n) ((struct varlena *) PG_GETARG_POINTER(n))
/* use this if you want the input datum de-toasted: */
diff --git a/src/include/portability/instr_time.h b/src/include/portability/instr_time.hindex 39a4f0600e..a78f0d284b 100644--- a/src/include/portability/instr_time.h+++ b/src/include/portability/instr_time.h@@ -141,6 +141,9 @@ typedef struct timespec instr_time;
#define INSTR_TIME_GET_MICROSEC(t) \
(((uint64) (t).tv_sec * (uint64) 1000000) + (uint64) ((t).tv_nsec / 1000))
+#define INSTR_TIME_GET_NANOSEC(t) \+ (((uint64) (t).tv_sec * (uint64) 1000000000) + (uint64) ((t).tv_nsec))+
#else /* !HAVE_CLOCK_GETTIME */
/* Use gettimeofday() */
@@ -205,6 +208,10 @@ typedef struct timeval instr_time;
#define INSTR_TIME_GET_MICROSEC(t) \
(((uint64) (t).tv_sec * (uint64) 1000000) + (uint64) (t).tv_usec)
+#define INSTR_TIME_GET_NANOSEC(t) \+ (((uint64) (t).tv_sec * (uint64) 1000000000) + \+ (uint64) (t).tv_usec * (uint64) 1000)+
#endif /* HAVE_CLOCK_GETTIME */
#else /* WIN32 */
@@ -237,6 +244,9 @@ typedef LARGE_INTEGER instr_time;
#define INSTR_TIME_GET_MICROSEC(t) \
((uint64) (((double) (t).QuadPart * 1000000.0) / GetTimerFrequency()))
+#define INSTR_TIME_GET_NANOSEC(t) \+ ((uint64) (((double) (t).QuadPart * 1000000000.0) / GetTimerFrequency()))+
static inline double
GetTimerFrequency(void)
{
diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.hindex a8f052e484..65d1e49fb2 100644--- a/src/include/storage/lwlock.h+++ b/src/include/storage/lwlock.h@@ -168,6 +168,7 @@ typedef enum BuiltinTrancheIds
LWTRANCHE_XACT_BUFFER = NUM_INDIVIDUAL_LWLOCKS,
LWTRANCHE_COMMITTS_BUFFER,
LWTRANCHE_SUBTRANS_BUFFER,
+ LWTRANCHE_CSN_LOG_BUFFERS,
LWTRANCHE_MULTIXACTOFFSET_BUFFER,
LWTRANCHE_MULTIXACTMEMBER_BUFFER,
LWTRANCHE_NOTIFY_BUFFER,
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.hindex be67d8a861..ade5d8e169 100644--- a/src/include/storage/proc.h+++ b/src/include/storage/proc.h@@ -15,12 +15,14 @@
#define _PROC_H_
#include "access/clog.h"
+#include "access/csn_snapshot.h"
#include "access/xlogdefs.h"
#include "lib/ilist.h"
#include "storage/latch.h"
#include "storage/lock.h"
#include "storage/pg_sema.h"
#include "storage/proclist_types.h"
+#include "utils/snapshot.h"
/*
* Each backend advertises up to PGPROC_MAX_CACHED_SUBXIDS TransactionIds
@@ -251,6 +253,18 @@ struct PGPROC
PGPROC *lockGroupLeader; /* lock group leader, if I'm a member */
dlist_head lockGroupMembers; /* list of members, if I'm a leader */
dlist_node lockGroupLink; /* my member link, if I'm a member */
++ /*+ * assignedCSN holds CSN for this transaction. It is generated+ * under a ProcArray lock and later is written to a CSNLog. This+ * variable defined as atomic only for case of group commit, in all other+ * scenarios only backend responsible for this proc entry is working with+ * this variable.+ */+ CSN_atomic assignedCSN;++ /* Original xmin of this backend before csn snapshot was imported */+ TransactionId originalXmin;
};
/* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */
diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.hindex b01fa52139..ba580435f9 100644--- a/src/include/storage/procarray.h+++ b/src/include/storage/procarray.h@@ -20,6 +20,10 @@
#include "utils/snapshot.h"
+#define PROCARRAY_NON_IMPORTED_XMIN 0x80 /* use originalXmin instead+ * of xmin to properly+ * maintain csnXidMap */+
extern Size ProcArrayShmemSize(void);
extern void CreateSharedProcArray(void);
extern void ProcArrayAdd(PGPROC *proc);
@@ -94,4 +98,7 @@ extern void ProcArraySetReplicationSlotXmin(TransactionId xmin,
extern void ProcArrayGetReplicationSlotXmin(TransactionId *xmin,
TransactionId *catalog_xmin);
+extern void ProcArraySetCSNSnapshotXmin(TransactionId xmin);++extern TransactionId ProcArrayGetCSNSnapshotXmin(void);
#endif /* PROCARRAY_H */
diff --git a/src/include/storage/sync.h b/src/include/storage/sync.hindex 6fd50cfa7b..eb1d52673a 100644--- a/src/include/storage/sync.h+++ b/src/include/storage/sync.h@@ -39,6 +39,7 @@ typedef enum SyncRequestHandler
SYNC_HANDLER_COMMIT_TS,
SYNC_HANDLER_MULTIXACT_OFFSET,
SYNC_HANDLER_MULTIXACT_MEMBER,
+ SYNC_HANDLER_CSN,
SYNC_HANDLER_NONE
} SyncRequestHandler;
diff --git a/src/include/utils/snapmgr.h b/src/include/utils/snapmgr.hindex c6a176cc95..122eea20ba 100644--- a/src/include/utils/snapmgr.h+++ b/src/include/utils/snapmgr.h@@ -41,10 +41,11 @@
&& !RelationIsAccessibleInLogicalDecoding(rel) \
)
-#define EarlyPruningEnabled(rel) (old_snapshot_threshold >= 0 && RelationAllowsEarlyPruning(rel))+#define EarlyPruningEnabled(rel) (old_snapshot_threshold >= 0 && !enable_csn_snapshot && RelationAllowsEarlyPruning(rel))
/* GUC variables */
extern PGDLLIMPORT int old_snapshot_threshold;
+extern PGDLLIMPORT bool enable_csn_snapshot;
extern Size SnapMgrShmemSize(void);
@@ -100,7 +101,7 @@ extern PGDLLIMPORT SnapshotData CatalogSnapshotData;
static inline bool
OldSnapshotThresholdActive(void)
{
- return old_snapshot_threshold >= 0;+ return (old_snapshot_threshold >= 0) && (!enable_csn_snapshot);
}
extern Snapshot GetTransactionSnapshot(void);
@@ -130,6 +131,8 @@ extern void AtSubCommit_Snapshot(int level);
extern void AtSubAbort_Snapshot(int level);
extern void AtEOXact_Snapshot(bool isCommit, bool resetXmin);
+extern SnapshotCSN ExportCSNSnapshot(void);+extern void ImportCSNSnapshot(SnapshotCSN snapshot_csn);
extern void ImportSnapshot(const char *idstr);
extern bool XactHasExportedSnapshots(void);
extern void DeleteAllExportedSnapshotFiles(void);
diff --git a/src/include/utils/snapshot.h b/src/include/utils/snapshot.hindex 6b60755c53..3580a94c43 100644--- a/src/include/utils/snapshot.h+++ b/src/include/utils/snapshot.h@@ -121,6 +121,9 @@ typedef enum SnapshotType
typedef struct SnapshotData *Snapshot;
#define InvalidSnapshot ((Snapshot) NULL)
+#define InvalidCSN ((CSN) 0)+typedef uint64 CSN;+typedef uint64 SnapshotCSN;
/*
* Struct representing all kind of possible snapshots.
@@ -214,6 +217,14 @@ typedef struct SnapshotData
* transactions completed since the last GetSnapshotData().
*/
uint64 snapXactCompletionCount;
++ /*+ * SnapshotCSN for snapshot isolation support.+ * Will be used only if enable_csn_snapshot is enabled.+ */+ SnapshotCSN snapshot_csn;+ /* Did we have our own snapshot_csn or imported one from different node */+ bool imported_csn;
} SnapshotData;
#endif /* SNAPSHOT_H */
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefileindex dffc79b2d9..16bb65e7e1 100644--- a/src/test/modules/Makefile+++ b/src/test/modules/Makefile@@ -7,6 +7,7 @@ include $(top_builddir)/src/Makefile.global
SUBDIRS = \
brin \
commit_ts \
+ csnsnapshot \
delay_execution \
dummy_index_am \
dummy_seclabel \
diff --git a/src/test/modules/csnsnapshot/Makefile b/src/test/modules/csnsnapshot/Makefilenew file mode 100644index 0000000000..15a07f8846--- /dev/null+++ b/src/test/modules/csnsnapshot/Makefile@@ -0,0 +1,22 @@+# src/test/modules/csnsnapshot/Makefile++NO_INSTALLCHECK = 1++TAP_TESTS = 1++# Doesn't support full consistency of distributed commit in READ COMMITTED+# transactions.+PROVE_TESTS = t/001_base.pl \+ t/002_standby.pl \+ t/003_parallel_safe.pl++ifdef USE_PGXS+PG_CONFIG = pg_config+PGXS := $(shell $(PG_CONFIG) --pgxs)+include $(PGXS)+else+subdir = src/test/modules/csnsnapshot+top_builddir = ../../../..+include $(top_builddir)/src/Makefile.global+include $(top_srcdir)/contrib/contrib-global.mk+endifdiff --git a/src/test/modules/csnsnapshot/expected/csnsnapshot.out b/src/test/modules/csnsnapshot/expected/csnsnapshot.outnew file mode 100644index 0000000000..ac28e417b6--- /dev/null+++ b/src/test/modules/csnsnapshot/expected/csnsnapshot.out@@ -0,0 +1 @@+create table t1(i int, j int, k varchar);diff --git a/src/test/modules/csnsnapshot/t/001_base.pl b/src/test/modules/csnsnapshot/t/001_base.plnew file mode 100644index 0000000000..b81419512e--- /dev/null+++ b/src/test/modules/csnsnapshot/t/001_base.pl@@ -0,0 +1,100 @@+use strict;+use warnings;++use PostgreSQL::Test::Cluster;+use PostgreSQL::Test::Utils;+use Test::More tests => 5;++my ($node, $test_snapshot, $count1, $count2);+$node = PostgreSQL::Test::Cluster->new('csntest');+$node->init;+$node->append_conf('postgresql.conf', qq{+ enable_csn_snapshot = on+ csn_snapshot_defer_time = 10+ max_prepared_transactions = 10+ });+$node->start;++# Create a table+$node->safe_psql('postgres', 'create table t1(i int, j int)');++# insert test record+$node->safe_psql('postgres', 'insert into t1 values(1,1)');+# export csn snapshot+$test_snapshot = $node->safe_psql('postgres', 'select pg_csn_snapshot_export()');+# insert test record+$node->safe_psql('postgres', 'insert into t1 values(2,1)');++$count1 = $node->safe_psql('postgres', "select count(*) from t1");+is($count1, '2', 'Get right number in normal query');+$count2 = $node->safe_psql('postgres', "+ begin transaction isolation level repeatable read;+ select pg_csn_snapshot_import($test_snapshot);+ select count(*) from t1;+ commit;"+ );++is($count2, '+1', 'Get right number in csn import query');++#prepare transaction test+$node->safe_psql('postgres', "+ begin;+ insert into t1 values(3,1);+ insert into t1 values(3,2);+ prepare transaction 'pt3';+ ");+$node->safe_psql('postgres', "+ begin;+ insert into t1 values(4,1);+ insert into t1 values(4,2);+ prepare transaction 'pt4';+ ");+$node->safe_psql('postgres', "+ begin;+ insert into t1 values(5,1);+ insert into t1 values(5,2);+ prepare transaction 'pt5';+ ");+$node->safe_psql('postgres', "+ begin;+ insert into t1 values(6,1);+ insert into t1 values(6,2);+ prepare transaction 'pt6';+ ");+$node->safe_psql('postgres', "commit prepared 'pt4';");++# restart with enable_csn_snapshot off+$node->append_conf('postgresql.conf', "enable_csn_snapshot = off");+$node->restart;+$node->safe_psql('postgres', "+ insert into t1 values(7,1);+ insert into t1 values(7,2);+ ");+$node->safe_psql('postgres', "commit prepared 'pt3';");+$count1 = $node->safe_psql('postgres', "select count(*) from t1");+is($count1, '8', 'Get right number in normal query');+++# restart with enable_csn_snapshot on+$node->append_conf('postgresql.conf', "enable_csn_snapshot = on");+$node->restart;+$node->safe_psql('postgres', "+ insert into t1 values(8,1);+ insert into t1 values(8,2);+ ");+$node->safe_psql('postgres', "commit prepared 'pt5';");+$count1 = $node->safe_psql('postgres', "select count(*) from t1");+is($count1, '12', 'Get right number in normal query');++# restart with enable_csn_snapshot off+$node->append_conf('postgresql.conf', "enable_csn_snapshot = on");+$node->restart;+$node->safe_psql('postgres', "+ insert into t1 values(9,1);+ insert into t1 values(9,2);+ ");+$node->safe_psql('postgres', "commit prepared 'pt6';");++$count1 = $node->safe_psql('postgres', "select count(*) from t1");+is($count1, '16', 'Get right number in normal query');diff --git a/src/test/modules/csnsnapshot/t/002_standby.pl b/src/test/modules/csnsnapshot/t/002_standby.plnew file mode 100644index 0000000000..27fcbb8f8a--- /dev/null+++ b/src/test/modules/csnsnapshot/t/002_standby.pl@@ -0,0 +1,68 @@+# Test simple scenario involving a standby++use strict;+use warnings;++use PostgreSQL::Test::Cluster;+use PostgreSQL::Test::Utils;+use Test::More tests => 6;++my ($master, $bkplabel, $standby, $guc_on_master, $guc_on_standby);++$bkplabel = 'backup';+$master = PostgreSQL::Test::Cluster->new('master');+$master->init(allows_streaming => 1);++$master->append_conf(+ 'postgresql.conf', qq{+ enable_csn_snapshot = on+ max_wal_senders = 5+ });+$master->start;+$master->backup($bkplabel);++$standby = PostgreSQL::Test::Cluster->new('standby');+$standby->init_from_backup($master, $bkplabel, has_streaming => 1);+$standby->start;++$master->safe_psql('postgres', "create table t1(i int, j int)");++$guc_on_master = $master->safe_psql('postgres', 'show enable_csn_snapshot');+is($guc_on_master, 'on', "GUC on master");++$guc_on_standby = $standby->safe_psql('postgres', 'show enable_csn_snapshot');+is($guc_on_standby, 'on', "GUC on standby");++$master->append_conf('postgresql.conf', 'enable_csn_snapshot = off');+$master->restart;++$guc_on_master = $master->safe_psql('postgres', 'show enable_csn_snapshot');+is($guc_on_master, 'off', "GUC off master");++$guc_on_standby = $standby->safe_psql('postgres', 'show enable_csn_snapshot');+is($guc_on_standby, 'on', "GUC on standby");++# We consume a large number of transaction,for skip page+for my $i (1 .. 4096) #4096+{+ $master->safe_psql('postgres', "insert into t1 values(1,$i)");+}+$master->safe_psql('postgres', "select pg_sleep(2)");+$master->append_conf('postgresql.conf', 'enable_csn_snapshot = on');+$master->restart;++my $count_standby = $standby->safe_psql('postgres', 'select count(*) from t1');+is($count_standby, '4096', "Ok for siwtch xid-base > csn-base"); #4096++# We consume a large number of transaction,for skip page+for my $i (1 .. 4096) #4096+{+ $master->safe_psql('postgres', "insert into t1 values(1,$i)");+}+$master->safe_psql('postgres', "select pg_sleep(2)");++$master->append_conf('postgresql.conf', 'enable_csn_snapshot = off');+$master->restart;++$count_standby = $standby->safe_psql('postgres', 'select count(*) from t1');+is($count_standby, '8192', "Ok for switch csn-base > xid-base"); #8192
\ No newline at end of file
diff --git a/src/test/modules/csnsnapshot/t/003_parallel_safe.pl b/src/test/modules/csnsnapshot/t/003_parallel_safe.plnew file mode 100644index 0000000000..e303e3f1a6--- /dev/null+++ b/src/test/modules/csnsnapshot/t/003_parallel_safe.pl@@ -0,0 +1,67 @@+# Check safety of CSN machinery for parallel mode.++use strict;+use warnings;++use PostgreSQL::Test::Cluster;+use PostgreSQL::Test::Utils;+use Test::More tests => 2;++my ($node, $updScr, $selScr, $started, $pgb_handle1, $result, $errors);++$node = PostgreSQL::Test::Cluster->new('csntest');+$node->init;+$node->append_conf('postgresql.conf', qq{+ enable_csn_snapshot = on+ csn_snapshot_defer_time = 10+ default_transaction_isolation = 'REPEATABLE READ'++ # force parallel mode.+ max_worker_processes = 64+ max_parallel_workers_per_gather = 16+ max_parallel_workers = 32+ parallel_setup_cost = 1+ parallel_tuple_cost = 0.05+ min_parallel_table_scan_size = 0+});+$node->start;++$node->command_ok([ 'pgbench', '-i', '-s', '1' ], "pgbench initialization ok");+$node->safe_psql('postgres', qq{+ CREATE OR REPLACE FUNCTION cnt() RETURNS integer AS '+ SELECT sum(abalance) FROM pgbench_accounts;+ ' LANGUAGE SQL PARALLEL SAFE COST 100000.;+});+++$updScr = File::Temp->new();+append_to_file($updScr, q{+ UPDATE pgbench_accounts SET abalance = abalance + 1 WHERE aid = 1;+});++$selScr = '+ SELECT count(*) AS res FROM (+ SELECT cnt() AS y FROM pgbench_accounts WHERE aid < 20+ GROUP BY (y)+ ) AS q;+';++# Launch updates+$pgb_handle1 = $node->pgbench_async(-n, -T => 10, -f => $updScr, 'postgres' );++$errors = 0;+$started = time();+while (time() - $started < 10)+{+ # Check that each worker returns the same sum on balance column.+ $result = $node->safe_psql('postgres', $selScr);+ if ($result ne 1)+ {+ $errors++;+ diag("Workers returned different sums: $result");+ }+}+is($errors, 0, 'isolation between UPDATE and concurrent SELECT workers.');++$node->pgbench_await($pgb_handle1);+$node->stop();
\ No newline at end of file
diff --git a/src/test/modules/snapshot_too_old/sto.conf b/src/test/modules/snapshot_too_old/sto.confindex 7eeaeeb0dc..3177cc0e15 100644--- a/src/test/modules/snapshot_too_old/sto.conf+++ b/src/test/modules/snapshot_too_old/sto.conf@@ -1,2 +1,3 @@
autovacuum = off
old_snapshot_threshold = 0
+enable_csn_snapshot = falsediff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pmindex 9467a199c8..9d38a4922d 100644--- a/src/test/perl/PostgreSQL/Test/Cluster.pm+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm@@ -2068,6 +2068,34 @@ sub pgbench
$self->command_checks_all(\@cmd, $stat, $out, $err, $name);
}
+sub pgbench_async()+{+ my ($self, @args) = @_;++ my ($in, $out, $err, $rc);+ $in = '';+ $out = '';++ my @pgbench_command = (+ 'pgbench',+ -h => $self->host,+ -p => $self->port,+ @args+ );+ my $handle = IPC::Run::start(\@pgbench_command, $in, $out);+ return $handle;+}++sub pgbench_await()+{+ my ($self, $pgbench_handle) = @_;++ # During run some pgbench threads can exit (for example due to+ # serialization error). That will set non-zero returning code.+ # So don't check return code here and leave it to a caller.+ my $rc = IPC::Run::finish($pgbench_handle);+}+
=pod
=item $node->connect_ok($connstr, $test_name, %params)
diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.outindex 2088857615..010b3b3144 100644--- a/src/test/regress/expected/sysviews.out+++ b/src/test/regress/expected/sysviews.out@@ -104,6 +104,8 @@ select name, setting from pg_settings where name like 'enable%';
--------------------------------+---------
enable_async_append | on
enable_bitmapscan | on
+ enable_csn_snapshot | on+ enable_csn_wal | on
enable_gathermerge | on
enable_hashagg | on
enable_hashjoin | on
@@ -122,7 +124,7 @@ select name, setting from pg_settings where name like 'enable%';
enable_seqscan | on
enable_sort | on
enable_tidscan | on
-(20 rows)+(22 rows)
-- Test that the pg_timezone_names and pg_timezone_abbrevs views are
-- more-or-less working. We can't test their contents in any great detail
--
2.25.1
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To: pgsql-hackers@postgresql.org
Cc: a.lepikhov@postgrespro.ru, masao.fujii@oss.nttdata.com, masahiko.sawada@2ndquadrant.com, amit.kapila16@gmail.com
Subject: Re: Global snapshots
In-Reply-To: <2983d675-7076-083a-aac7-b35d84c7d6ff@postgrespro.ru>
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