TiFlash is reporting errors and restarting continuously. [ERROR]: Detected overflow when decoding integer of length 22 with column type UInt64: pk_type is INT64, schema_snapshot->col_id_to_block_pos

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

drop table test.tm_test;

CREATE TABLE `test`.`tm_test` (
  `id` bigint NOT NULL,
  `customer_types` json DEFAULT NULL,
  `other_phones` varchar(1024) DEFAULT NULL,
  PRIMARY KEY (`id`) /*T![clustered_index] CLUSTERED */,
  KEY `idx_customer_profile_customer_types` ((cast(`customer_types` as unsigned array)))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin COMMENT='测试表';

INSERT INTO test.tm_test (id,customer_types,other_phones) VALUES
	 (40343892505477852,'[1, 0]',NULL),
	 (40343892505477907,'[1]',NULL),
	 (40343892505477915,'[1, 0]',NULL),
	 (40343892505477919,'[1]',NULL),
	 (40564894342709282,'[1, 0]',NULL),
	 (40564894342709318,'[1, 0]',NULL),
	 (40564894342709322,'[1]',NULL),
	 (40564894342709326,'[0]',NULL),
	 (40610284294152202,'[3]',NULL),
	 (40610284294152208,'[0]',''),
	 (40610284294152218,'[1, 0]',NULL),
	 (40610284294152242,'[1]',NULL),
	 (40617455906889734,'[1, 0]',NULL);

ALTER TABLE test.tm_test SET TIFLASH REPLICA 1;
select * from information_schema.tiflash_replica;

ALTER TABLE test.tm_test MODIFY COLUMN other_phones varchar(512) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NULL;

2. What did you expect to see? (Required)

[2026/01/27 19:31:09.217 +08:00] [ERROR] [RaftCommands.cpp:506] ["[region_id=742705 applied_term=6 applied_index=8] catch exception: Detected overflow when decoding integer of length 35 with column type UInt64: pk_type is INT64, schema_snapshot->col_id_to_block_pos is  [map info : (column_id=-1025, pos=2) (column_id=-1024, pos=1) (column_id=-1, pos=0) (column_id=1, pos=3) (column_id=2, pos=4) (column_id=4, pos=6) (column_id=5, pos=5)  ];, schema_snapshot->col_id_to_def_pos is  [map info : (column_id=-1025, pos=2) (column_id=-1024, pos=1) (column_id=-1, pos=0) (column_id=1, pos=3) (column_id=2, pos=4) (column_id=4, pos=6) (column_id=5, pos=5)  ];,schema_snapshot->column_defines is  [column define : (id=-1, name=_tidb_rowid, type=Int64) (id=-1024, name=_INTERNAL_VERSION, type=UInt64) (id=-1025, name=_INTERNAL_DELMARK, type=UInt8) (id=1, name=id, type=Int64) (id=2, name=customer_types, type=Nullable(String)) (id=5, name=other_phones, type=Nullable(String)) (id=4, name=_v$_idx_customer_profile_customer_types_0, type=Nullable(UInt64))  ];, decoding_snapshot_epoch is 2, block schema is [{\"name\":\"_INTERNAL_DELMARK\",\"id\":-1025,\"type\":\"UInt8\",\"column\":\"UInt8(size = 1)\"},{\"name\":\"_INTERNAL_VERSION\",\"id\":-1024,\"type\":\"UInt64\",\"column\":\"UInt64(size = 1)\"},{\"name\":\"_tidb_rowid\",\"id\":-1,\"type\":\"Int64\",\"column\":\"Int64(size = 0)\"},{\"name\":\"id\",\"id\":1,\"type\":\"Int64\",\"column\":\"Int64(size = 0)\"},{\"name\":\"customer_types\",\"id\":2,\"type\":\"Nullable(String)\",\"column\":\"Nullable(size = 1, String(size = 1), UInt8(size = 1))\"},{\"name\":\"_v$_idx_customer_profile_customer_types_0\",\"id\":4,\"type\":\"Nullable(UInt64)\",\"column\":\"Nullable(size = 0, UInt64(size = 0), UInt8(size = 0))\"},{\"name\":\"other_phones\",\"id\":5,\"type\":\"Nullable(String)\",\"column\":\"Nullable(size = 0, String(size = 0), UInt8(size = 0))\"}] : TiKV value contains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

3. What did you see instead (Required)

4. What is your TiFlash version? (Required)

V8.5.4

Start with the SQL reproduction on TiFlash V8.5.4 and inspect the failure reported at RaftCommands.cpp:506. Trace the integer decoding involving pk_type INT64 and schema_snapshot column mappings; done means the ALTER TABLE operation no longer produces the overflow error or repeated restarts.