Fix pg_dump for hash partitioning on enum columns

Automatic partition handling: Auto-enables --load-via-partition-root when dumping partitioned tables with hash partitioning on enum types to prevent partition constraint violations after dump/reload cycles
Parallel restore safety: Modifies pg_restore to skip TRUNCATE operations when partition root loading is detected, eliminating deadlocks and data loss risks
Dump metadata enhancement: Adds special comment markers for TABLE DATA items using partition root loading mode
Documentation update: Removes obsolete warning about --load-via-partition-root with parallel restore from pg_dump documentation

Author: 付与龙10336563

src/bin/pg_dump/pg_dump.c

@@ -2806,7 +2806,7 @@ dumpTableData(Archive *fout, const TableDataInfo *tdinfo)
 
 	    parentTbinfo = getRootTableInfo(tbinfo);
 	    copyFrom = fmtQualifiedDumpable(parentTbinfo);
-	    printfPQExpBuffer(copyBuf, "-- load via partition root %s",
+	    printfPQExpBuffer(copyBuf, "--load-via-partition-root %s",
 	                      copyFrom);
 	    tdDefn = pg_strdup(copyBuf->data);
 	}

src/bin/pg_dump/pg_dump.h

@@ -341,7 +341,7 @@ typedef struct _tableInfo
 	bool		dummy_view;		/* view's real definition must be postponed */
 	bool		postponed_def;	/* matview must be postponed into post-data */
 	bool		ispartition;	/* is table a partition? */
-	bool        unsafe_partitions;  /* is it an unsafe partitioned table? */
+	bool		unsafe_partitions;  /* is it an unsafe partitioned table? */
 
 	/*
 	 * These fields are computed only if we decide the table is interesting

src/bin/pg_dump/t/004_pg_dump_parallel.pl

@@ -0,0 +1,78 @@
+use strict;
+use warnings;
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my $dbname1 = 'regression_src';
+my $dbname2 = 'regression_dest1';
+my $dbname3 = 'regression_dest2';
+
+my $node = PostgreSQL::Test::Cluster->new('main');
+$node->init;
+$node->start;
+
+my $backupdir = $node->backup_dir;
+
+$node->run_log([ 'createdb', $dbname1 ]);
+$node->run_log([ 'createdb', $dbname2 ]);
+$node->run_log([ 'createdb', $dbname3 ]);
+
+$node->safe_psql(
+   $dbname1,
+   qq{
+create type digit as enum ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9');
+
+-- plain table with index
+create table tplain (en digit, data int unique);
+insert into tplain select (x%10)::text::digit, x from generate_series(1,1000) x;
+
+-- non-troublesome hashed partitioning
+create table ths (mod int, data int, unique(mod, data)) partition by hash(mod);
+create table ths_p1 partition of ths for values with (modulus 3, remainder 0);
+create table ths_p2 partition of ths for values with (modulus 3, remainder 1);
+create table ths_p3 partition of ths for values with (modulus 3, remainder 2);
+insert into ths select (x%10), x from generate_series(1,1000) x;
+
+-- dangerous hashed partitioning
+create table tht (en digit, data int, unique(en, data)) partition by hash(en);
+create table tht_p1 partition of tht for values with (modulus 3, remainder 0);
+create table tht_p2 partition of tht for values with (modulus 3, remainder 1);
+create table tht_p3 partition of tht for values with (modulus 3, remainder 2);
+insert into tht select (x%10)::text::digit, x from generate_series(1,1000) x;
+   });
+
+$node->command_ok(
+   [
+       'pg_dump', '-Fd', '--no-sync', '-j2', '-f', "$backupdir/dump1",
+       $node->connstr($dbname1)
+   ],
+   'parallel dump');
+
+$node->command_ok(
+   [
+       'pg_restore', '-v',
+       '-d',         $node->connstr($dbname2),
+       '-j3',        "$backupdir/dump1"
+   ],
+   'parallel restore');
+
+$node->command_ok(
+   [
+       'pg_dump',   '-Fd',
+       '--no-sync', '-j2',
+       '-f',        "$backupdir/dump2",
+       '--inserts', $node->connstr($dbname1)
+   ],
+   'parallel dump as inserts');
+
+$node->command_ok(
+   [
+       'pg_restore', '-v',
+       '-d',         $node->connstr($dbname3),
+       '-j3',        "$backupdir/dump2"
+   ],
+   'parallel restore as inserts');
+
+done_testing();