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Add pg_dump --snapshot option

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Allows pg_dump to use a snapshot previously defined by a concurrent
session that has either used pg_export_snapshot() or obtained a
snapshot when creating a logical slot. When this option is used with
parallel pg_dump, the snapshot defined by this option is used and no
new snapshot is taken.

Simon Riggs and Michael Paquier
This commit is contained in:
Simon Riggs 2014-11-17 22:15:07 +00:00
parent 832054044f
commit be1cc8f46f
2 changed files with 55 additions and 17 deletions
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21
doc/src/sgml/ref/pg_dump.sgml
View File

@ -847,6 +847,27 @@ PostgreSQL documentation
</listitem>
</varlistentry>
<varlistentry>
<term><option>--snapshot=<replaceable class="parameter">snapshotname</replaceable></option></term>
<listitem>
<para>
Use the specifed synchronized snapshot when making a dump of the
database (see
<xref linkend="functions-snapshot-synchronization-table"> for more
details).
</para>
<para>
This option is useful when needing to synchronize the dump with
a logical replication slot (see <xref linkend="logicaldecoding">)
or with a concurrent session.
</para>
<para>
In the case of a parallel dump, the snapshot name defined by this
option is used rather than taking a new snapshot.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--serializable-deferrable</option></term>
<listitem>

51
src/bin/pg_dump/pg_dump.c
View File

@ -126,7 +126,8 @@ static const CatalogId nilCatalogId = {0, 0};
static void help(const char *progname);
static void setup_connection(Archive *AH, DumpOptions *dopt,
const char *dumpencoding, char *use_role);
const char *dumpencoding, const char *dumpsnapshot,
char *use_role);
static ArchiveFormat parseArchiveFormat(const char *format, ArchiveMode *mode);
static void expand_schema_name_patterns(Archive *fout,
SimpleStringList *patterns,
@ -269,6 +270,7 @@ main(int argc, char **argv)
RestoreOptions *ropt;
Archive *fout; /* the script file */
const char *dumpencoding = NULL;
const char *dumpsnapshot = NULL;
char *use_role = NULL;
int numWorkers = 1;
trivalue prompt_password = TRI_DEFAULT;
@ -329,6 +331,7 @@ main(int argc, char **argv)
{"role", required_argument, NULL, 3},
{"section", required_argument, NULL, 5},
{"serializable-deferrable", no_argument, &dopt->serializable_deferrable, 1},
{"snapshot", required_argument, NULL, 6},
{"use-set-session-authorization", no_argument, &dopt->use_setsessauth, 1},
{"no-security-labels", no_argument, &dopt->no_security_labels, 1},
{"no-synchronized-snapshots", no_argument, &dopt->no_synchronized_snapshots, 1},
@ -506,6 +509,10 @@ main(int argc, char **argv)
set_dump_section(optarg, &dopt->dumpSections);
break;
case 6: /* snapshot */
dumpsnapshot = pg_strdup(optarg);
break;
default:
fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
exit_nicely(1);
@ -614,7 +621,7 @@ main(int argc, char **argv)
* death.
*/
ConnectDatabase(fout, dopt->dbname, dopt->pghost, dopt->pgport, dopt->username, prompt_password);
setup_connection(fout, dopt, dumpencoding, use_role);
setup_connection(fout, dopt, dumpencoding, dumpsnapshot, use_role);
/*
* Disable security label support if server version < v9.1.x (prevents
@ -658,6 +665,11 @@ main(int argc, char **argv)
"Run with --no-synchronized-snapshots instead if you do not need\n"
"synchronized snapshots.\n");
/* check the version when a snapshot is explicitly specified by user */
if (dumpsnapshot && fout->remoteVersion < 90200)
exit_horribly(NULL,
"Exported snapshots are not supported by this server version.\n");
/* Find the last built-in OID, if needed */
if (fout->remoteVersion < 70300)
{
@ -888,6 +900,7 @@ help(const char *progname)
printf(_(" --quote-all-identifiers quote all identifiers, even if not key words\n"));
printf(_(" --section=SECTION dump named section (pre-data, data, or post-data)\n"));
printf(_(" --serializable-deferrable wait until the dump can run without anomalies\n"));
printf(_(" --snapshot=SNAPSHOT use given synchronous snapshot for the dump\n"));
printf(_(" --use-set-session-authorization\n"
" use SET SESSION AUTHORIZATION commands instead of\n"
" ALTER OWNER commands to set ownership\n"));
@ -907,7 +920,8 @@ help(const char *progname)
}
static void
setup_connection(Archive *AH, DumpOptions *dopt, const char *dumpencoding, char *use_role)
setup_connection(Archive *AH, DumpOptions *dopt, const char *dumpencoding,
const char *dumpsnapshot, char *use_role)
{
PGconn *conn = GetConnection(AH);
const char *std_strings;
@ -1015,22 +1029,25 @@ setup_connection(Archive *AH, DumpOptions *dopt, const char *dumpencoding, char
ExecuteSqlStatement(AH,
"SET TRANSACTION ISOLATION LEVEL SERIALIZABLE");
/*
* define an export snapshot, either chosen by user or needed for
* parallel dump.
*/
if (dumpsnapshot)
AH->sync_snapshot_id = strdup(dumpsnapshot);
if (AH->numWorkers > 1 && AH->remoteVersion >= 90200 && !dopt->no_synchronized_snapshots)
if (AH->sync_snapshot_id)
{
if (AH->sync_snapshot_id)
{
PQExpBuffer query = createPQExpBuffer();
appendPQExpBufferStr(query, "SET TRANSACTION SNAPSHOT ");
appendStringLiteralConn(query, AH->sync_snapshot_id, conn);
ExecuteSqlStatement(AH, query->data);
destroyPQExpBuffer(query);
}
else
AH->sync_snapshot_id = get_synchronized_snapshot(AH);
PQExpBuffer query = createPQExpBuffer();
appendPQExpBuffer(query, "SET TRANSACTION SNAPSHOT ");
appendStringLiteralConn(query, AH->sync_snapshot_id, conn);
ExecuteSqlStatement(AH, query->data);
destroyPQExpBuffer(query);
}
else if (AH->numWorkers > 1 &&
AH->remoteVersion >= 90200 &&
!dopt->no_synchronized_snapshots)
AH->sync_snapshot_id = get_synchronized_snapshot(AH);
if (AH->remoteVersion >= 90500)
{
@ -1044,7 +1061,7 @@ setup_connection(Archive *AH, DumpOptions *dopt, const char *dumpencoding, char
static void
setupDumpWorker(Archive *AHX, DumpOptions *dopt, RestoreOptions *ropt)
{
setup_connection(AHX, dopt, NULL, NULL);
setup_connection(AHX, dopt, NULL, NULL, NULL);
}
static char *