More defensive, add caveats

README.md

@@ -1,7 +1,17 @@
-# parquet-vtable
+# sqlite-parquet-vtable
 
 A SQLite [virtual table](https://sqlite.org/vtab.html) extension to expose Parquet files as SQL tables.
 
+## Caveats
+
+I'm not a professional C/C++ programmer. These are the caveats I'm aware of, but there are probably others:
+
+* I don't use `sqlite3_malloc` and `sqlite3_free` for C++ objects
+  * Maybe this doesn't matter, since portability isn't a goal
+* The C (SQLite API implementation) -> C++ interop (to talk to parquet-cpp) probably leaks some C++ exceptions
+  * Your process may crash due to my error. Sorry!
+  * I handle the obvious cases like file not found and unsupported Parquet types but I suspect low memory conditions aren't handled gracefully
+
 ## Building
 
 1. Install [`parquet-cpp`](https://github.com/apache/parquet-cpp)
@@ -18,3 +28,26 @@ sqlite> create virtual table demo USING parquet('demo.parquet');
 sqlite> select * from demo limit 1;
 ...if all goes well, you'll see data here!...
 ```
+
+## Supported features
+
+### Index
+
+Only full table scans are supported.
+
+### Types
+
+These types are supported:
+
+* INT96 timestamps (exposed as milliseconds since the epoch)
+* INT8/INT16/INT32/INT64
+* UTF8 strings
+* BOOLEAN
+* FLOAT
+* DOUBLE
+
+These are not supported:
+
+* UINT8/UINT16/UINT32/UINT64
+* Fixed length byte arrays, including JSON and BSON subtypes
+* DECIMAL