feat: add global system tables framework under sys database

[suxiaogang223]

Summary

Add global system table support under the sys database, enabling catalog-level metadata queries.

Closes part of #141.

Changes

Infrastructure

• Add GetOptions() to Catalog interface for catalog-level config access
• FileSystemCatalog stores and exposes catalog options
• New GlobalSystemTableLoader with independent registry for sys tables
• Extend SystemTablePath with is_global flag and TryParsePath to detect sys/ paths
• FileSystemCatalog handles sys database in ListTables/DatabaseExists/TableExists/LoadTableSchema

Global System Tables

Table	Status	Columns
sys.catalog_options	✅ Complete	key, value
sys.all_table_options	✅ Complete	database_name, table_name, key, value
sys.tables	✅ Complete	database_name, table_name, table_type, partitioned, primary_key, record_count, file_size_in_bytes, file_count, last_file_creation_time
sys.partitions	✅ Complete	database_name, table_name, partition_name, record_count, file_size_in_bytes, file_count, last_update_time

Integration Tests (4 new tests in SystemTableReadInteTest)

• TestReadGlobalCatalogOptions — verifies schema + content
• TestReadGlobalAllTableOptions — verifies table options across databases
• TestReadGlobalTables — verifies schema, table metadata
• TestReadGlobalPartitions — verifies empty result for unpartitioned tables

Files Changed

 include/paimon/catalog/catalog.h                   |   5 +
 src/paimon/CMakeLists.txt                          |   1 +
 src/paimon/core/catalog/catalog.cpp                |   2 +-
 src/paimon/core/catalog/file_system_catalog.cpp    |  39 +-
 src/paimon/core/catalog/file_system_catalog.h      |   6 +-
 .../core/table/system/global_system_tables.cpp     | 370 ++++++++++++++
 .../core/table/system/global_system_tables.h       | 117 +++++
 src/paimon/core/table/system/system_table.cpp      |  28 +-
 src/paimon/core/table/system/system_table.h        |   2 +
 .../core/catalog/file_system_catalog_test.cpp      |  14 +-
 test/inte/read_inte_test.cpp                       | 237 +++++++++
 11 files changed, 810 insertions(+), 10 deletions(-)

Verification

Fedora x86_64, GCC 16:

• Build: ✅
• paimon-core-test: 36/40 pass (4 failures pre-existing)
• paimon-read-inte-test (global tables): 4/4 ✅
• paimon-read-inte-test (system tables): same as before

🤖 Generated with Claude Code

[zjw1111]

Thanks a lot for building out the global sys system tables — the loader/registry split and reuse of InMemorySystemTable make the design clean and easy to follow.

I left a few inline comments. The most important one is a potential crash on the normal engine read path for sys.tables / sys.partitions / sys.all_table_options (see the comment in system_table.cpp). A couple of smaller notes are below:

• global_system_tables.cpp (CatalogOptionsSystemTable::BuildRows, around line 264): this table stores fields via a non-owning std::string_view into context_.catalog_options, while the other tables copy through BinaryString (StringValue). It's safe today because the map is a stable member, but for consistency and to avoid a future dangling-view footgun, would it be possible to use StringValue(...) here too?
• file_system_catalog.cpp (line 282): the const_cast<FileSystemCatalog*>(this) looks unnecessary since only const Catalog methods are used later — declaring GlobalSystemTableContext::catalog as const Catalog* would let you drop it. Minor, feel free to skip.

Thanks again!

[zjw1111]

One additional inline note on the sys.tables primary_key column — a schema/data-contract nit. Thanks!

[lxy-9602]

+1

[zjw1111]

Thanks again for the updates. Two small consistency notes on the new sys.tables implementation versus Java Paimon.

[zjw1111]

Thanks for aligning the sys.tables schema with Java — the 14-column layout looks great.

One small consistency issue on the default table_type: here it falls back to "TABLE" (uppercase), but Java's AllTablesTable uses options.getOrDefault(TYPE.key(), TYPE.defaultValue().toString()), and TableType.TABLE.toString() returns the lowercase "table" (see TableType: TABLE("table", ...)). So for a normal table without an explicit type option, the C++ reader emits "TABLE" while Java emits "table", which clients relying on the Java contract would see as a mismatch.

Would it be possible to default to the lowercase "table"? Note that TestReadGlobalTables currently asserts "TABLE", so that assertion would need updating as well.

[zjw1111]

Thanks for populating the file statistics here.

I wonder if this diverges from Java's contract for a filesystem catalog. In Java, CatalogUtils.toTableAndSnapshots only loads a TableSnapshot when catalog.supportsVersionManagement() is true; FileSystemCatalog (via AbstractCatalog) returns false, so snapshot stays null and AllTablesTable emits null for record_count / file_size_in_bytes / file_count / last_file_creation_time. This PR instead reads the latest snapshot and manifests to compute them, so for a table with committed data the C++ reader returns non-null values where Java returns null.

In addition, the semantics of record_count itself differ: here it is the sum of row_count over merged ADD entries (i.e. live rows), whereas Java's snapshot.recordCount() is the accumulated totalRecordCount, so even when populated the two are not equivalent.

TestReadGlobalTables doesn't surface this because the tables have no committed data (empty snapshot → all-null branch). Could you clarify whether this is an intentional enhancement? If so, it would help to document the difference from the Java FS-catalog contract in a comment and add a "table with data" case to lock in the expected values.