feat(shredding): Add infrastructure for shared-shredding MAP storage layout (#348)

Author: lxy-9602

include/paimon/defs.h

@@ -365,6 +365,21 @@ struct PAIMON_EXPORT Options {
     /// "partition.legacy-name" - The legacy partition name is using `ToString` for all types. If
     /// false, using casting to string for all types. Default value is "true".
     static const char PARTITION_GENERATE_LEGACY_NAME[];
+    /// "map.storage-layout" - Suffix for per-column MAP storage layout configuration.
+    /// Used as `fields.<column>.map.storage-layout`. Values: "default" (standard KV arrays)
+    /// or "shared-shredding" (columnar shredding with column reuse). Default is "default".
+    /// If set "shared-shredding", the column must be of type MAP<STRING, T>. Each column must be
+    /// configured individually. For example, to enable shared-shredding layout for two columns
+    /// "metrics" and "tags":
+    ///   fields.metrics.map.storage-layout = shared-shredding
+    ///   fields.tags.map.storage-layout = shared-shredding
+    static const char MAP_STORAGE_LAYOUT[];
+    /// "map.shared-shredding.max-columns" - Suffix for per-column upper bound K_max configuration.
+    /// Used as `fields.<column>.map.shared-shredding.max-columns`. Only effective when
+    /// map.storage-layout = shared-shredding. Rows with more fields than K_max spill to
+    /// __overflow. Default value is 256. Each column can have its own max-columns setting.
+    static const char MAP_SHARED_SHREDDING_MAX_COLUMNS[];
+
     /// "blob-as-descriptor" - Read blob field using blob descriptor rather than blob
     /// bytes. Default value is "false".
     static const char BLOB_AS_DESCRIPTOR[];

src/paimon/CMakeLists.txt

@@ -137,6 +137,7 @@ set(PAIMON_COMMON_SRCS
     common/utils/bloom_filter64.cpp
     common/utils/crc32c.cpp
     common/utils/decimal_utils.cpp
+    common/data/shredding/map_shared_shredding_utils.cpp
     common/utils/delta_varint_compressor.cpp
     common/utils/fields_comparator.cpp
     common/utils/path_util.cpp
@@ -531,6 +532,7 @@ if(PAIMON_BUILD_TESTS)
                     common/utils/decimal_utils_test.cpp
                     common/utils/threadsafe_queue_test.cpp
                     common/utils/generic_lru_cache_test.cpp
+                    common/data/shredding/map_shared_shredding_utils_test.cpp
                     STATIC_LINK_LIBS
                     paimon_shared
                     test_utils_static