扩展架构

-- Unqualified lookup
SELECT complex_abs(value) FROM table;

-- Qualified lookup
SELECT vsql_complex.complex_abs(value) FROM table;

extension_name.veb (tar archive)
├── manifest.json       # Extension metadata (required)
└── lib/
    └── extension.so    # Compiled shared library (required)

{
  "name": "extension_name",          // Required: lowercase_with_underscores
  "version": "1.0.0",                // Required: semantic version
  "description": "Brief description",
  "author": "Your Name",
  "license": "GPL-2.0"
}

INSTALL EXTENSION name
    ↓
1. Validate .veb exists in veb_dir
    ↓
2. Calculate SHA256 hash of .veb
    ↓
3. Expand to {datadir}/.veb_expansion_cache/{name}/{sha256}/
    ↓
4. Parse and validate manifest.json
    ↓
5. Load .so library (dlopen with RTLD_LOCAL)
    ↓
6. Call vef_register() entry point
    ↓
7. Register VDFs and custom types
    ↓
8. Persist registration and update cache
    ↓
Success

UNINSTALL EXTENSION name
    ↓
1. Check for column dependencies
    ↓
2. Call vef_unregister() cleanup hook
    ↓
3. Drop registered VDFs
    ↓
4. Drop custom types
    ↓
5. Remove extension registration and update cache
    ↓
6. Unload .so library (dlclose)
    ↓
7. Keep .veb_expansion_cache directory (for reinstall)
    ↓
Success

datadir/
└── .veb_expansion_cache/
    └── extension_name/
        ├── abc123.../              # SHA256 of v1.0.0 .veb
        │   ├── manifest.json
        │   └── lib/extension.so
        └── def456.../              # SHA256 of v2.0.0 .veb
            ├── manifest.json
            └── lib/extension.so

SystemTableMap<ExtensionEntry> m_extensions;
SystemTableMap<CustomTypeEntry> m_types;
SystemTableMap<CustomColumnEntry> m_columns;
SystemTableMap<PropertyEntry> m_properties;

CREATE TABLE t (col COMPLEX)
    ↓
1. Parser encounters COMPLEX
    ↓
2. PT_custom_type::create()
    ↓
3. ResolveTypeToContext(extension_name, type_name)
    ↓
4. VictionaryClient::lookup_type() → O(log n)
    ↓
5. Find TypeDescriptor in cache
    ↓
6. Create Field with implementation_type

-- Slow: VDF call per row
SELECT * FROM signals WHERE complex_abs(impedance) > 100;

-- Fast: Computed column with index
ALTER TABLE signals
ADD COLUMN impedance_magnitude DOUBLE AS (complex_abs(impedance)) STORED,
ADD INDEX(impedance_magnitude);

SELECT * FROM signals WHERE impedance_magnitude > 100;

1. Open each VillageSQL system table
2. Check column count and names
3. Validate column types
4. Verify primary keys
5. Check indexes

SELECT VERSION();

8.4.9-villagesql-0.0.4