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Add ALTER SUBSCRIPTION ... SKIP.

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This feature allows skipping the transaction on subscriber nodes.

If incoming change violates any constraint, logical replication stops
until it's resolved. Currently, users need to either manually resolve the
conflict by updating a subscriber-side database or by using function
pg_replication_origin_advance() to skip the conflicting transaction. This
commit introduces a simpler way to skip the conflicting transactions.

The user can specify LSN by ALTER SUBSCRIPTION ... SKIP (lsn = XXX),
which allows the apply worker to skip the transaction finished at
specified LSN. The apply worker skips all data modification changes within
the transaction.

Author: Masahiko Sawada
Reviewed-by: Takamichi Osumi, Hou Zhijie, Peter Eisentraut, Amit Kapila, Shi Yu, Vignesh C, Greg Nancarrow, Haiying Tang, Euler Taveira
Discussion: https://postgr.es/m/CAD21AoDeScrsHhLyEPYqN3sydg6PxAPVBboK=30xJfUVihNZDA@mail.gmail.com
This commit is contained in:
Amit Kapila
2022-03-22 07:11:19 +05:30
parent 315ae75e9b
commit 208c5d65bb
18 changed files with 665 additions and 173 deletions
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73
src/backend/commands/subscriptioncmds.c
View File

@ -45,6 +45,7 @@
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/pg_lsn.h"
#include "utils/syscache.h"
/*
@ -62,6 +63,7 @@
#define SUBOPT_STREAMING 0x00000100
#define SUBOPT_TWOPHASE_COMMIT 0x00000200
#define SUBOPT_DISABLE_ON_ERR 0x00000400
#define SUBOPT_LSN 0x00000800
/* check if the 'val' has 'bits' set */
#define IsSet(val, bits) (((val) & (bits)) == (bits))
@ -84,6 +86,7 @@ typedef struct SubOpts
bool streaming;
bool twophase;
bool disableonerr;
XLogRecPtr lsn;
} SubOpts;
static List *fetch_table_list(WalReceiverConn *wrconn, List *publications);
@ -262,6 +265,33 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
opts->specified_opts |= SUBOPT_DISABLE_ON_ERR;
opts->disableonerr = defGetBoolean(defel);
}
else if (IsSet(supported_opts, SUBOPT_LSN) &&
strcmp(defel->defname, "lsn") == 0)
{
char *lsn_str = defGetString(defel);
XLogRecPtr lsn;
if (IsSet(opts->specified_opts, SUBOPT_LSN))
errorConflictingDefElem(defel, pstate);
/* Setting lsn = NONE is treated as resetting LSN */
if (strcmp(lsn_str, "none") == 0)
lsn = InvalidXLogRecPtr;
else
{
/* Parse the argument as LSN */
lsn = DatumGetLSN(DirectFunctionCall1(pg_lsn_in,
CStringGetDatum(lsn_str)));
if (XLogRecPtrIsInvalid(lsn))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid WAL location (LSN): %s", lsn_str)));
}
opts->specified_opts |= SUBOPT_LSN;
opts->lsn = lsn;
}
else
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
@ -479,6 +509,7 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
LOGICALREP_TWOPHASE_STATE_PENDING :
LOGICALREP_TWOPHASE_STATE_DISABLED);
values[Anum_pg_subscription_subdisableonerr - 1] = BoolGetDatum(opts.disableonerr);
values[Anum_pg_subscription_subskiplsn - 1] = LSNGetDatum(InvalidXLogRecPtr);
values[Anum_pg_subscription_subconninfo - 1] =
CStringGetTextDatum(conninfo);
if (opts.slot_name)
@ -1106,6 +1137,48 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
break;
}
case ALTER_SUBSCRIPTION_SKIP:
{
parse_subscription_options(pstate, stmt->options, SUBOPT_LSN, &opts);
/* ALTER SUBSCRIPTION ... SKIP supports only LSN option */
Assert(IsSet(opts.specified_opts, SUBOPT_LSN));
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to skip transaction")));
/*
* If the user sets subskiplsn, we do a sanity check to make
* sure that the specified LSN is a probable value.
*/
if (!XLogRecPtrIsInvalid(opts.lsn))
{
RepOriginId originid;
char originname[NAMEDATALEN];
XLogRecPtr remote_lsn;
snprintf(originname, sizeof(originname), "pg_%u", subid);
originid = replorigin_by_name(originname, false);
remote_lsn = replorigin_get_progress(originid, false);
/* Check the given LSN is at least a future LSN */
if (!XLogRecPtrIsInvalid(remote_lsn) && opts.lsn < remote_lsn)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("skip WAL location (LSN %X/%X) must be greater than origin LSN %X/%X",
LSN_FORMAT_ARGS(opts.lsn),
LSN_FORMAT_ARGS(remote_lsn))));
}
values[Anum_pg_subscription_subskiplsn - 1] = LSNGetDatum(opts.lsn);
replaces[Anum_pg_subscription_subskiplsn - 1] = true;
update_tuple = true;
break;
}
default:
elog(ERROR, "unrecognized ALTER SUBSCRIPTION kind %d",
stmt->kind);