Synchronize access to Connection, Statement and ResultSet

This change adds synchronization between accessing and deleting
underlying native objects for `Connection`, `Statement` and
`ResultSet`. All synchronization is done in JNI part, Java-level
synchronization is removed from a few places where it was used.
`volatile` fields are added when checking whether the object is closed
or not.

`Connection`'s underlying native object maintains a list of `Statement`s
currently open on this `Connection`. These statements are closed when
the connection is closed. Running queries are cancelled (interrupted)
automatically when the `Connection` is closed.

Note: `Statement.close()` is blocked if a long query, that was started
from this statement, is still running. `Statement.cancel()` must be
called manually before calling `close()` to perform the closing
promptly. This cannot be done automatically, because `cancel()` is
implemented in the engine as a `Connection`-level operation, thus
calling `cancel()` on a `Statement` can interrupt the query running
on another `Statement` on the same `Connection`.

Synchronization for `Appender` is going to be added in a separate PR.

Testing: new tests added for various sequential and concurrent closure
scenarios.

Fixes: duckdb#101

Author: staticlibs

CMakeLists.txt

@@ -439,7 +439,7 @@ set(DUCKDB_SRC_FILES
   src/duckdb/extension/json/json_serializer.cpp
   src/duckdb/ub_extension_json_json_functions.cpp)
 
-set(JEMACLLOC_SRC_FILES 
+set(JEMALLOC_SRC_FILES 
   src/duckdb/extension/jemalloc/jemalloc_extension.cpp
   src/duckdb/extension/jemalloc/jemalloc/src/jemalloc.c
   src/duckdb/extension/jemalloc/jemalloc/src/arena.c
@@ -553,13 +553,14 @@ add_jar(duckdb_jdbc_tests ${JAVA_TEST_FILES} INCLUDE_JARS duckdb_jdbc)
 if(MSVC)
   list(APPEND DUCKDB_SRC_FILES duckdb_java.def)
 else()
-  list(APPEND DUCKDB_SRC_FILES ${JEMACLLOC_SRC_FILES})
+  list(APPEND DUCKDB_SRC_FILES ${JEMALLOC_SRC_FILES})
 endif()
 
 add_library(duckdb_java SHARED
   src/jni/config.cpp
   src/jni/duckdb_java.cpp
   src/jni/functions.cpp
+  src/jni/holders.cpp
   src/jni/refs.cpp
   src/jni/types.cpp
   src/jni/util.cpp

CMakeLists.txt.in

@@ -46,7 +46,7 @@ set(DUCKDB_DEFINITIONS
 set(DUCKDB_SRC_FILES 
   ${SOURCES})
 
-set(JEMACLLOC_SRC_FILES 
+set(JEMALLOC_SRC_FILES 
   ${JEMALLOC_SOURCES})
 
 
@@ -95,13 +95,14 @@ add_jar(duckdb_jdbc_tests ${JAVA_TEST_FILES} INCLUDE_JARS duckdb_jdbc)
 if(MSVC)
   list(APPEND DUCKDB_SRC_FILES duckdb_java.def)
 else()
-  list(APPEND DUCKDB_SRC_FILES ${JEMACLLOC_SRC_FILES})
+  list(APPEND DUCKDB_SRC_FILES ${JEMALLOC_SRC_FILES})
 endif()
 
 add_library(duckdb_java SHARED
   src/jni/config.cpp
   src/jni/duckdb_java.cpp
   src/jni/functions.cpp
+  src/jni/holders.cpp
   src/jni/refs.cpp
   src/jni/types.cpp
   src/jni/util.cpp

duckdb_java.def

@@ -34,6 +34,7 @@ Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1auto_1commit
 Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1catalog
 Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1schema
 Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1interrupt
+Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1is_1result_1open
 Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1prepare
 Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1prepared_1statement_1meta
 Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1query_1result_1meta

duckdb_java.exp

@@ -31,6 +31,7 @@ _Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1auto_1commit
 _Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1catalog
 _Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1schema
 _Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1interrupt
+_Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1is_1result_1open
 _Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1prepare
 _Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1prepared_1statement_1meta
 _Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1query_1result_1meta

duckdb_java.map

@@ -33,6 +33,7 @@ DUCKDB_JAVA {
     Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1catalog;
     Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1get_1schema;
     Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1interrupt;
+    Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1is_1result_1open;
     Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1prepare;
     Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1prepared_1statement_1meta;
     Java_org_duckdb_DuckDBNative_duckdb_1jdbc_1query_1result_1meta;