Merge variegata into main pt 1 (duckdb#453)

Build works again, lots of integration fixes and one small refactor of
pyarrow and polars pushdown to use the expression API.

Author: evertlammerts

CMakeLists.txt

@@ -57,6 +57,11 @@ target_include_directories(
   INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src/duckdb_py/include>
 )
 
+# We link duckdb_static. Without this define, duckdb.h marks C API symbols
+# __declspec(dllimport) on Windows, producing unresolvable __imp_* references at
+# link time. No-op on non-Windows.
+target_compile_definitions(_duckdb_dependencies INTERFACE DUCKDB_STATIC_BUILD)
+
 # ────────────────────────────────────────────
 # Descend into the real DuckDB‑Python sources
 # ────────────────────────────────────────────
@@ -81,37 +86,6 @@ pybind11_add_module(
 target_link_libraries(_duckdb PRIVATE _duckdb_dependencies)
 duckdb_link_extensions(_duckdb)
 
-# ────────────────────────────────────────────
-# Controlling symbol export
-#
-# We want to export exactly two symbols: - PyInit__duckdb: this allows CPython
-# to load the module - duckdb_adbc_init: the DuckDB ADBC driver
-#
-# The export of symbols on OSX and Linux is controlled by: - Visibility
-# annotations in the code (for this lib we use the PYBIND11_EXPORT macro) -
-# Telling the linker which symbols we want exported, which we do below
-#
-# For Windows, we rely on just the visbility annotations.
-# ────────────────────────────────────────────
-set_target_properties(
-  _duckdb
-  PROPERTIES CXX_VISIBILITY_PRESET hidden
-             C_VISIBILITY_PRESET hidden
-             VISIBILITY_INLINES_HIDDEN ON)
-
-if(APPLE)
-  target_link_options(
-    _duckdb PRIVATE "LINKER:-exported_symbol,_duckdb_adbc_init"
-    "LINKER:-exported_symbol,_PyInit__duckdb")
-elseif(UNIX AND NOT APPLE)
-  target_link_options(
-    _duckdb PRIVATE "LINKER:--export-dynamic-symbol=duckdb_adbc_init"
-    "LINKER:--export-dynamic-symbol=PyInit__duckdb")
-elseif(WIN32)
-  target_link_options(_duckdb PRIVATE "/EXPORT:duckdb_adbc_init"
-                      "/EXPORT:PyInit__duckdb")
-endif()
-
 # ────────────────────────────────────────────
 # Put the object file in the correct place
 # ────────────────────────────────────────────