make ext_engine: duckdb to work

Makefile

@@ -5,7 +5,7 @@ Defines =
 CC = $(CXX) -xc 
 CXXFLAGS = --std=c++2a
 ifeq ($(AQ_DEBUG), 1)
-	OPTFLAGS = -g3 #-static-libasan -fsanitize=address 
+	OPTFLAGS = -g3 #-static-libsan -fsanitize=address 
 	LINKFLAGS = 
 else
 	OPTFLAGS = -Ofast -DNDEBUG -fno-stack-protector 
@@ -17,12 +17,15 @@ _COMPILER = $(shell $(CXX) --version | grep -q clang && echo clang|| echo gcc)
 COMPILER = $(strip $(_COMPILER))
 LIBTOOL = ar rcs
 USELIB_FLAG = -Wl,--whole-archive,libaquery.a -Wl,-no-whole-archive
-LIBAQ_SRC = server/monetdb_conn.cpp server/libaquery.cpp 
-LIBAQ_OBJ = monetdb_conn.o libaquery.o monetdb_ext.o
+LIBAQ_SRC = server/monetdb_conn.cpp server/duckdb_conn.cpp server/libaquery.cpp 
+LIBAQ_OBJ = monetdb_conn.o duckdb_conn.o libaquery.o monetdb_ext.o
 SEMANTIC_INTERPOSITION = -fno-semantic-interposition
 RANLIB = ranlib
 _LINKER_BINARY = $(shell `$(CXX) -print-prog-name=ld` -v 2>&1 | grep -q LLVM && echo lld || echo ld)
 LINKER_BINARY = $(strip $(_LINKER_BINARY))
+DuckDB_LIB = -Ldeps -lduckdb
+DuckDB_INC = -Ideps
+
 ifeq ($(LINKER_BINARY), ld)
 	LINKER_FLAGS = -Wl,--allow-multiple-definition
 else
@@ -58,6 +61,7 @@ ifeq ($(OS),Windows_NT)
 	LIBAQ_OBJ += winhelper.o
 	MonetDB_LIB += msc-plugin/monetdbe.dll 
 	MonetDB_INC +=  -Imonetdb/msvc
+	
 	LIBTOOL = gcc-ar rcs
 	ifeq ($(COMPILER), clang)
 		FPIC =
@@ -96,8 +100,8 @@ ifeq ($(AQUERY_ITC_USE_SEMPH), 1)
 	Defines += -D__AQUERY_ITC_USE_SEMPH__
 endif
 
-CXXFLAGS += $(OPTFLAGS) $(Defines) $(MonetDB_INC) 
-BINARYFLAGS = $(CXXFLAGS) $(LINKFLAGS) $(MonetDB_LIB)
+CXXFLAGS += $(OPTFLAGS) $(Defines) $(MonetDB_INC) $(DuckDB_INC) 
+BINARYFLAGS = $(CXXFLAGS) $(LINKFLAGS) $(MonetDB_LIB) $(DuckDB_LIB)
 SHAREDFLAGS += $(FPIC) $(BINARYFLAGS)
 
 info:

aquery_config.py

@@ -2,7 +2,7 @@
 
 ## GLOBAL CONFIGURATION FLAGS
 
-version_string = '0.7.5a'
+version_string = '0.7.6a'
 add_path_to_ldpath = True
 rebuild_backend = False
 run_backend = True
@@ -12,6 +12,8 @@ msbuildroot = ''
 os_platform = 'unknown'
 build_driver = 'Auto'
 compilation_output = True
+compile_use_gc = True
+compile_use_threading = True
 
 ## END GLOBAL CONFIGURATION FLAGS
 

build.py

@@ -75,14 +75,15 @@ class build_manager:
     sourcefiles = [
                    'build.py', 'Makefile', 
                    'server/server.cpp', 'server/libaquery.cpp',  
-                   'server/monetdb_conn.cpp', 'server/threading.cpp', 
-                   'server/winhelper.cpp', 'server/monetdb_ext.c'
+                   'server/monetdb_conn.cpp', 'server/duckdb_conn.cpp',
+                   'server/threading.cpp', 'server/winhelper.cpp', 
+                   'server/monetdb_ext.c'
                    ]
     headerfiles = ['server/aggregations.h', 'server/hasher.h', 'server/io.h', 
-                   'server/libaquery.h', 'server/monetdb_conn.h', 'server/pch.hpp', 
-                   'server/table.h', 'server/threading.h', 'server/types.h', 'server/utils.h', 
-                   'server/winhelper.h', 'server/gc.h', 'server/vector_type.hpp', 
-                   'server/table_ext_monetdb.hpp' 
+                   'server/libaquery.h', 'server/monetdb_conn.h', 'server/duckdb_conn.h', 
+                   'server/pch.hpp', 'server/table.h', 'server/threading.h', 
+                   'server/types.h', 'server/utils.h', 'server/winhelper.h', 
+                   'server/gc.h', 'server/vector_type.hpp', 'server/table_ext_monetdb.hpp' 
                    ]
    
     class DriverBase:

common/ast.py

@@ -229,6 +229,7 @@ class Context:
         self.removing_scan = False
 
     def __init__(self): 
+        from prompt import PromptState
         self.tables:list[TableInfo] = []
         self.tables_byname = dict()
         self.ccols_byname = dict()
@@ -252,6 +253,9 @@ class Context:
         self.ds_stack = []
         self.scans = []
         self.removing_scan = False
+        self.force_compiled = True
+        self.system_state: Optional[PromptState] = None
+        
     def add_table(self, table_name, cols):
         tbl = TableInfo(table_name, cols, self)
         self.tables.append(tbl)

common/types.py

@@ -31,7 +31,7 @@ class Types:
             self.name = name
             self.cname = defval(cname, name.lower() + '_t')
             self.sqlname = defval(sqlname, name.upper())
-            self.ctype_name = defval(ctype_name, f'types::{name.upper()}') 
+            self.ctype_name = defval(ctype_name, f'types::A{name.upper()}') 
             self.null_value = defval(null_value, 0)
             self.cast_to_dict = defval(cast_to, dict())
             self.cast_from_dict = defval(cast_from, dict())
@@ -102,7 +102,7 @@ LongT = Types(4, name = 'int64', sqlname = 'BIGINT', fp_type = DoubleT)
 BoolT = Types(0, name = 'bool', cname='bool', sqlname = 'BOOL', long_type=LongT, fp_type=FloatT)
 ByteT = Types(1, name = 'int8', sqlname = 'TINYINT', long_type=LongT, fp_type=FloatT)
 ShortT = Types(2, name = 'int16', sqlname='SMALLINT', long_type=LongT, fp_type=FloatT)
-IntT = Types(3, name = 'int', cname = 'int', long_type=LongT, fp_type=FloatT)
+IntT = Types(3, name = 'int', cname = 'int', long_type=LongT, ctype_name = 'types::AINT32', fp_type=FloatT)
 ULongT = Types(8, name = 'uint64', sqlname = 'UINT64', fp_type=DoubleT)
 UIntT = Types(7, name = 'uint32', sqlname = 'UINT32', long_type=ULongT, fp_type=FloatT)
 UShortT = Types(6, name = 'uint16', sqlname = 'UINT16', long_type=ULongT, fp_type=FloatT)

demo/action.cpp

@@ -20,7 +20,7 @@ __AQEXPORT__(int) action(Context* cxt) {
     if (fit_inc == nullptr)
         fit_inc = (decltype(fit_inc))(cxt->get_module_function("fit_inc"));
 
-	auto server = static_cast<Server*>(cxt->alt_server);
+	auto server = static_cast<DataSource*>(cxt->alt_server);
     auto len = uint32_t(monetdbe_get_size(*((void**)server->server), "source"));
     auto x_1bN = ColRef<vector_type<double>>(len, monetdbe_get_col(*((void**)(server->server)), "source", 0));
     auto y_6uX = ColRef<int64_t>(len, monetdbe_get_col(*((void**)(server->server)), "source", 1));

demo/putdata.cpp

@@ -23,7 +23,7 @@ __AQEXPORT__(int) ld(Context* cxt) {
 	else
 		++cnt;
 	char data_name[] = "data/electricity/electricity       ";
-	auto server = static_cast<Server*>(cxt->alt_server);
+	auto server = static_cast<DataSource*>(cxt->alt_server);
 	const char* names_fZrv[] = {"x", "y"};
 	auto tbl_6erF = new TableInfo<vector_type<double>,int64_t>("source", names_fZrv);
 	decltype(auto) c_31ju0e = tbl_6erF->get_col<0>();

demo/query.cpp

@@ -16,7 +16,7 @@ __AQEXPORT__(void) __AQ_Init_GC__(Context* cxt) {
 __AQEXPORT__(int) query(Context* cxt) {
 	using namespace std;
 	using namespace types;
-    auto server = static_cast<Server*>(cxt->alt_server);
+    auto server = static_cast<DataSource*>(cxt->alt_server);
     static uint32_t old_sz = 0;
     constexpr static uint32_t min_delta = 200;
     auto newsz = monetdbe_get_size(*(void**) server->server, "source");

engine/__init__.py

@@ -1,4 +1,4 @@
-from reconstruct.ast import Context, ast_node
+from engine.ast import Context, ast_node
 
 saved_cxt = None
 

engine/ast.py

@@ -6,7 +6,7 @@ from typing import Dict, List, Optional, Set, Tuple, Union
 from common.types import *
 from common.utils import (base62alp, base62uuid, enlist, 
                           get_innermost, get_legal_name)
-from reconstruct.storage import ColRef, Context, TableInfo
+from engine.storage import ColRef, Context, TableInfo
 
 class ast_node:
     header = []
@@ -51,7 +51,7 @@ class ast_node:
             self.emit(self.sql+';\n')
             self.context.sql_end()
         
-from reconstruct.expr import expr, fastscan
+from engine.expr import expr, fastscan
 class SubqType(Enum):
     WITH = auto()
     FROM = auto()
@@ -328,7 +328,7 @@ class projection(ast_node):
         for v, idx in self.var_table.items():
             vname = get_legal_name(v) + '_' + base62uuid(3)
             self.pyname2cname[v] = vname
-            self.context.emitc(f'auto {vname} = ColRef<{typenames[idx].cname}>({length_name}, server->getCol({idx}));')
+            self.context.emitc(f'auto {vname} = ColRef<{typenames[idx].cname}>({length_name}, server->getCol({idx}, {typenames[idx].ctype_name}));')
             vid2cname[idx] = vname
         # Create table into context
         out_typenames = [None] * len(proj_map)
@@ -463,7 +463,7 @@ class select_into(ast_node):
             raise Exception('No out_table found.')
         else:
             self.context.headers.add('"./server/table_ext_monetdb.hpp"')
-            self.ccode = f'{self.parent.out_table.contextname_cpp}->monetdb_append_table(cxt->alt_server, \"{node.lower()}\");'
+            self.ccode = f'{self.parent.out_table.contextname_cpp}->monetdb_append_table(cxt->curr_server, \"{node.lower()}\");'
             
     def produce_sql(self, node):
         self.context.sql = self.context.sql.replace(
@@ -1252,6 +1252,7 @@ class load(ast_node):
     name="load"
     first_order = name
     def init(self, node):
+        from prompt import Backend_Type
         self.module = False
         if node['load']['file_type'] == 'module':
             self.produce = self.produce_module
@@ -1259,8 +1260,10 @@ class load(ast_node):
         elif 'complex' in node['load']:
             self.produce = self.produce_cpp
             self.consume = lambda *_: None
-        elif self.context.dialect == 'MonetDB':
+        elif self.context.system_state.cfg.backend_type == Backend_Type.BACKEND_MonetDB.value:
             self.produce = self.produce_monetdb
+        elif self.context.system_state.cfg.backend_type == Backend_Type.BACKEND_DuckDB.value:
+            self.produce = self.produce_duckdb
         else: 
             self.produce = self.produce_aq
         if self.parent is None:
@@ -1328,6 +1331,15 @@ class load(ast_node):
         if 'term' in node:
             self.sql += f' {s3} \'{node["term"]["literal"]}\''
     
+    def produce_duckdb(self, node):
+        node = node['load']
+        s1 = f'COPY {node["table"]} FROM '
+        import os
+        p = os.path.abspath(node['file']['literal']).replace('\\', '/')
+        s2 = f" DELIMITER '{node['term']['literal']}', " if 'term' in node else ''
+        self.sql = f'{s1} \'{p}\' ( {s2}HEADER )'
+        
+    
     def produce_cpp(self, node):
         self.context.has_dll = True
         self.context.headers.add('"csv.h"')
@@ -1374,7 +1386,7 @@ class load(ast_node):
             
         self.context.emitc('}')
         # self.context.emitc(f'print(*{self.out_table});')
-        self.context.emitc(f'{self.out_table}->monetdb_append_table(cxt->alt_server, "{table.table_name}");')
+        self.context.emitc(f'{self.out_table}->monetdb_append_table(cxt->curr_server, "{table.table_name}");')
         
         self.context.postproc_end(self.postproc_fname)
 
@@ -1424,7 +1436,11 @@ class outfile(ast_node):
         file_pointer = 'fp_' + base62uuid(6)
         self.addc(f'FILE* {file_pointer} = fopen("{filename}", "wb");')
         self.addc(f'{self.parent.out_table.contextname_cpp}->printall("{sep}", "\\n", nullptr, {file_pointer});')
+        if self.context.use_gc:
+            self.addc(f'GC::gc_handle->reg({file_pointer}, 65536, [](void* fp){{fclose((FILE*)fp);}});')
+        else:
             self.addc(f'fclose({file_pointer});')  
+            
         self.context.ccode += self.ccode
 
 class udf(ast_node):

engine/expr.py

@@ -1,8 +1,8 @@
 from typing import Optional, Set
 
 from common.types import *
-from reconstruct.ast import ast_node
-from reconstruct.storage import ColRef, Context
+from engine.ast import ast_node
+from engine.storage import ColRef, Context
 
 # TODO: Decouple expr and upgrade architecture
 # C_CODE : get ccode/sql code?
@@ -31,7 +31,7 @@ class expr(ast_node):
         return self._udf_decltypecall is not None
     
     def __init__(self, parent, node, *, c_code = None, supress_undefined = False):
-        from reconstruct.ast import projection, udf
+        from engine.ast import projection, udf
 
         # gen2 expr have multi-passes
         # first pass parse json into expr tree
@@ -80,7 +80,7 @@ class expr(ast_node):
         ast_node.__init__(self, parent, node, None)
 
     def init(self, _):
-        from reconstruct.ast import _tmp_join_union, projection
+        from engine.ast import _tmp_join_union, projection
         parent = self.parent
         self.is_compound = parent.is_compound if type(parent) is expr else False
         if type(parent) in [projection, expr, _tmp_join_union]:
@@ -96,7 +96,7 @@ class expr(ast_node):
         
     def produce(self, node):
         from common.utils import enlist
-        from reconstruct.ast import udf, projection
+        from engine.ast import udf, projection
         
         if type(node) is dict:
             if 'literal' in node:
@@ -349,7 +349,7 @@ class expr(ast_node):
                 self.sql = f'{{"CAST({node} AS DOUBLE)" if not c_code else "{node}f"}}'
                 
     def finalize(self, override = False):
-        from reconstruct.ast import udf
+        from engine.ast import udf
         if self.codebuf is None or override:
             self.codebuf = ''
             for c in self.codlets:

engine/new_expr.py

@@ -1,7 +1,7 @@
 import abc
-from reconstruct.ast import ast_node
+from engine.ast import ast_node
 from typing import Optional 
-from reconstruct.storage import Context, ColRef
+from engine.storage import Context, ColRef
 from common.utils import enlist
 from common.types import builtin_func, user_module_func, builtin_operators
 
@@ -47,7 +47,7 @@ class expr_base(ast_node, metaclass = abc.ABCMeta):
         pass
     
     def produce(self, node):
-        from reconstruct.ast import udf
+        from engine.ast import udf
         if node and type(node) is dict:
             if 'litral' in node:
                 self.get_literal(node['literal'])

engine/storage.py

@@ -1,4 +1,4 @@
-from typing import Dict, List, Set
+from typing import Dict, List, Optional, Set
 
 from common.types import *
 from common.utils import CaseInsensitiveDict, base62uuid, enlist
@@ -64,7 +64,7 @@ class ColRef:
 
 class TableInfo:
     def __init__(self, table_name, cols, cxt:'Context'):
-        from reconstruct.ast import create_trigger
+        from engine.ast import create_trigger
         # statics
         self.table_name : str = table_name
         self.contextname_cpp : str = ''
@@ -161,8 +161,10 @@ class Context:
         self.has_dll = False
         self.triggers_active.clear()
         
-    def __init__(self):
+    def __init__(self, state = None):
+        from prompt import PromptState
         from .ast import create_trigger
+        from aquery_config import compile_use_gc
         self.tables_byname : Dict[str, TableInfo] = dict()
         self.col_byname = dict()
         self.tables : Set[TableInfo] = set()
@@ -181,6 +183,10 @@ class Context:
         self.triggers : Dict[str, create_trigger] = dict()
         self.triggers_active = set()
         self.stored_proceudres = dict()
+        self.force_compiled = False
+        self.use_gc = compile_use_gc 
+        self.system_state: Optional[PromptState] = state 
+
         # self.new() called everytime new query batch is started
 
     def get_scan_var(self):
@@ -206,7 +212,7 @@ class Context:
     function_head = ('(Context* cxt) {\n' +
         '\tusing namespace std;\n' +
         '\tusing namespace types;\n' + 
-        '\tauto server = static_cast<Server*>(cxt->alt_server);\n')
+        '\tauto server = static_cast<DataSource*>(cxt->curr_server);\n')
     
     udf_head = ('#pragma once\n'
         '#include \"./server/libaquery.h\"\n'
@@ -265,7 +271,7 @@ class Context:
             'O' + limit + sep + end)
         
     def remove_trigger(self, name : str):
-        from reconstruct.ast import create_trigger
+        from engine.ast import create_trigger
         val = self.triggers.pop(name, None)
         if val.type == create_trigger.Type.Callback:
             val.table.triggers.remove(val)

mem_opt.cpp

@@ -17,7 +17,7 @@ __AQEXPORT__(void) __AQ_Init_GC__(Context* cxt) {
 __AQEXPORT__(int) dll_2Cxoox(Context* cxt) {
 	using namespace std;
 	using namespace types;
-	auto server = static_cast<Server*>(cxt->alt_server);
+	auto server = static_cast<DataSource*>(cxt->alt_server);
 auto len_4ycjiV = server->cnt;
 auto mont_8AE = ColRef<const char*>(len_4ycjiV, server->getCol(0));
 auto sales_2RB = ColRef<int>(len_4ycjiV, server->getCol(1));

msc-plugin/libaquery.vcxproj

@@ -345,6 +345,7 @@
   <ItemGroup>
     <ClInclude Include="..\csv.h" />
     <ClInclude Include="..\server\aggregations.h" />
+    <ClInclude Include="..\server\DataSource_conn.h" />
     <ClInclude Include="..\server\duckdb_conn.h" />
     <ClInclude Include="..\server\gc.h" />
     <ClInclude Include="..\server\hasher.h" />

prompt.py

@@ -82,7 +82,6 @@ if __name__ == '__main__':
         exit()
 
     
-    
 import atexit
 import ctypes
 import enum
@@ -95,7 +94,7 @@ import sys
 import threading
 import time
 from dataclasses import dataclass
-from typing import Callable, List, Optional
+from typing import Callable, List, Optional, Union
 
 import numpy as np
 from mo_parsing import ParseException
@@ -104,10 +103,10 @@ import aquery_parser as parser
 import common
 import common.ddl
 import common.projection
-import reconstruct as xengine
+import engine as xengine
 from build import build_manager
 from common.utils import add_dll_dir, base62uuid, nullstream, ws
-
+from enum import auto
 
 ## CLASSES BEGIN
 class RunType(enum.Enum):
@@ -118,6 +117,16 @@ class Backend_Type(enum.Enum):
     BACKEND_AQuery = 0
     BACKEND_MonetDB = 1
     BACKEND_MariaDB = 2
+    BACKEND_DuckDB = 3
+    BACKEND_SQLite = 4
+    BACKEND_TOTAL = 5
+backend_strings = {
+    'aquery': Backend_Type.BACKEND_AQuery,
+    'monetdb': Backend_Type.BACKEND_MonetDB,
+    'mariadb': Backend_Type.BACKEND_MariaDB,
+    'duckdb': Backend_Type.BACKEND_DuckDB,
+    'sqlite': Backend_Type.BACKEND_SQLite,
+}
 
 class StoredProcedure(ctypes.Structure):
     _fields_ = [
@@ -242,7 +251,7 @@ class PromptState():
     set_ready = lambda: None
     get_ready = lambda: None
     server_status = lambda: False
-    cfg : Config = None
+    cfg : Optional[Config] = None
     shm : str = ''
     server : subprocess.Popen = None
     basecmd : List[str] = None
@@ -257,6 +266,26 @@ class PromptState():
     currstats : Optional[QueryStats] = None
     buildmgr : Optional[build_manager]= None
     current_procedure : Optional[str] = None
+    _force_compiled : bool = False
+    _cxt : Optional[Union[xengine.Context, common.Context]] = None
+    @property 
+    def force_compiled(self):
+        return self._force_compiled
+
+    @force_compiled.setter 
+    def force_compiled(self, new_val): 
+        self.cxt.force_compiled = new_val
+        self._force_compiled = new_val
+        
+    @property 
+    def cxt(self):
+        return self._cxt
+
+    @cxt.setter 
+    def cxt(self, cxt):
+        cxt.force_compiled = self.force_compiled
+        self._cxt = cxt
+        self._cxt.system_state = self
 ## CLASSES END
 
 ## FUNCTIONS BEGIN
@@ -412,7 +441,8 @@ def prompt(running = lambda:True, next = lambda:input('> '), state : Optional[Pr
     q = ''
     payload = None
     keep = True
-    cxt = common.initialize()
+    
+    state.cxt = cxt = xengine.initialize()
     parser.parse('SELECT "**** WELCOME TO AQUERY++! ****";')
     
     # state.currstats = QueryStats()
@@ -442,7 +472,7 @@ def prompt(running = lambda:True, next = lambda:input('> '), state : Optional[Pr
                 continue
             if False and q == 'exec': # generate build and run (AQuery Engine)
                 state.cfg.backend_type = Backend_Type.BACKEND_AQuery.value
-                cxt = common.exec(state.stmts, cxt, keep)
+                state.cxt = cxt = common.exec(state.stmts, cxt, keep)
                 if state.buildmgr.build_dll() == 0:
                     state.set_ready()
                 continue
@@ -466,8 +496,8 @@ def prompt(running = lambda:True, next = lambda:input('> '), state : Optional[Pr
                     print(prompt_help)
                 continue
             elif q.startswith('xexec') or q.startswith('exec'): # generate build and run (MonetDB Engine)
-                state.cfg.backend_type = Backend_Type.BACKEND_MonetDB.value
-                cxt = xengine.exec(state.stmts, cxt, keep, parser.parse)
+                #state.cfg.backend_type = Backend_Type.BACKEND_MonetDB.value
+                state.cxt = cxt = xengine.exec(state.stmts, cxt, keep, parser.parse)
                 
                 this_udf = cxt.finalize_udf()
                 if this_udf:
@@ -659,6 +689,20 @@ def prompt(running = lambda:True, next = lambda:input('> '), state : Optional[Pr
                 else:
                     print(procedure_help)
                 continue
+            elif q.startswith('force'):
+                splits = q.split()
+                if len(splits > 1) and splits[1] == 'compiled': 
+                    state.force_compiled = True
+                    cxt.force_compiled = True
+                continue
+            elif q.startswith('backend'):
+                splits = q.split()
+                if len(splits) > 1 and splits[1] in backend_strings:
+                    state.cfg.backend_type = backend_strings[splits[1]].value
+                else:
+                    cxt.Error('Not a valid backend type.')
+                print('External Engine is set to', Backend_Type(state.cfg.backend_type).name)
+                continue
             trimed = ws.sub(' ', og_q).split(' ') 
             if len(trimed) > 1 and trimed[0].lower().startswith('fi') or trimed[0].lower() == 'f':
                 fn = 'stock.a' if len(trimed) <= 1 or len(trimed[1]) == 0 \

server/DataSource_conn.h

@@ -2,24 +2,32 @@
 #define __DATASOURCE_CONN_H__
 struct Context;
 
+#ifndef __AQQueryResult__
+#define __AQQueryResult__ 1
 struct AQQueryResult {
     void* res;
     unsigned ref;
 };
-enum DataSourceType {
-    Invalid, 
-    MonetDB, 
-    MariaDB, 
-    DuckDB, 
-    SQLite
+#endif
+
+#ifndef __AQBACKEND_TYPE__
+#define __AQBACKEND_TYPE__ 1
+enum Backend_Type {
+	BACKEND_AQuery,
+	BACKEND_MonetDB,
+	BACKEND_MariaDB, 
+	BACKEND_DuckDB,
+	BACKEND_SQLite,
+	BACKEND_TOTAL
 };
+#endif
 
 struct DataSource {
     void* server = nullptr;
     Context* cxt = nullptr;
     bool status = false;
     char* query = nullptr;
-    DataSourceType type = Invalid;
+    Backend_Type DataSourceType = BACKEND_AQuery;
 
     void* res = nullptr;
     void* ret_col = nullptr;
@@ -29,7 +37,7 @@ struct DataSource {
     void* handle;
 
     DataSource() = default;
-    explicit DataSource(Context* cxt = nullptr) = delete;
+    explicit DataSource(Context* cxt) = delete;
     
     virtual void connect(Context* cxt) = 0;
     virtual void exec(const char* q) = 0;
@@ -38,6 +46,10 @@ struct DataSource {
     virtual void close() = 0;
     virtual bool haserror() = 0;
     // virtual void print_results(const char* sep = " ", const char* end = "\n");
-    virtual ~DataSource() = 0;
+    virtual ~DataSource() {};
 };
+// TODO: replace with super class
+//typedef DataSource* (*create_server_t)(Context* cxt);
+typedef void* (*create_server_t)(Context* cxt);
+void* CreateNULLServer(Context*);
 #endif //__DATASOURCE_CONN_H__

server/duckdb_conn.cpp

@@ -11,7 +11,8 @@ void DuckdbServer::connect(Context* cxt) {
 		static_cast<duckdb_database*>(malloc(sizeof(duckdb_database)));
 	this->handle = db_handle;
 	bool status = duckdb_open(nullptr, db_handle);
-	duckdb_connection* conn_handle;
+	duckdb_connection* conn_handle = 
+		static_cast<duckdb_connection*>(malloc(sizeof(duckdb_connection)));;
 	status = status || duckdb_connect(*db_handle, conn_handle);
 	this->server = conn_handle;
 	if (status != 0) {
@@ -20,6 +21,7 @@ void DuckdbServer::connect(Context* cxt) {
 }
 
 DuckdbServer::DuckdbServer(Context* cxt) {
+	this->DataSourceType = BACKEND_DuckDB;
 	this->cxt = cxt;
 	connect(cxt);
 }

server/duckdb_conn.h

@@ -3,7 +3,7 @@
 #include "DataSource_conn.h"
 
 struct DuckdbServer : DataSource {
-    explicit DuckdbServer(Context* cxt = nullptr);
+    explicit DuckdbServer(Context* cxt);
     void connect(Context* cxt);
     void exec(const char* q);
     void* getCol(int col_idx, int type);

server/libaquery.cpp

@@ -633,3 +633,5 @@ get_procedure(Context* cxt, const char* name) {
         };
     return res->second;
 }
+
+void* CreateNULLServer(Context*) { return nullptr; }

server/libaquery.h

@@ -63,11 +63,17 @@ enum Log_level {
 	LOG_SILENT
 };
 
+#ifndef __AQBACKEND_TYPE__
+#define __AQBACKEND_TYPE__ 1
 enum Backend_Type {
 	BACKEND_AQuery,
 	BACKEND_MonetDB,
-	BACKEND_MariaDB
+	BACKEND_MariaDB, 
+	BACKEND_DuckDB,
+	BACKEND_SQLite,
+	BACKEND_TOTAL
 };
+#endif
 
 struct QueryStats{
 	long long monet_time;
@@ -81,10 +87,14 @@ struct Config{
     int buffer_sizes[];
 };
 
+#ifndef __AQQueryResult__
+#define __AQQueryResult__ 1
 struct AQQueryResult {
     void* res;
-	uint32_t ref;
+    unsigned ref;
 };
+#endif
+
 
 struct Session{
     struct Statistic{
@@ -114,7 +124,8 @@ struct Context {
 	int n_buffers, *sz_bufs;
 	void **buffers;
 
-	void* alt_server = nullptr;
+	void* curr_server;
+	void* alt_server[BACKEND_TOTAL] = {nullptr};
 	Log_level log_level = LOG_INFO;
 
 	Session current;

server/mariadb_conn.cpp

@@ -9,7 +9,7 @@ inline size_t my_strlen(const char* str){
     return ret;
 }
 
-void Server::connect(
+void MariadbServer::connect(
     Context* cxt, const char* host, const char* user, const char* passwd, 
         const char* db_name, const unsigned int port, 
         const char* unix_socket, const unsigned long client_flag
@@ -35,12 +35,12 @@ void Server::connect(
     this->status = true;
 }
 
-void Server::exec(const char*q){
+void MariadbServer::exec(const char*q){
     auto res = mysql_real_query(server, q, my_strlen(q));
     if(res) printf("Execution Error: %d, %s\n", res, mysql_error(server)); 
 }
 
-void Server::close(){
+void MariadbServer::close(){
     if(this->status && this->server){
         mysql_close(server);
         server = 0;

server/mariadb_conn.h

@@ -5,7 +5,7 @@
 #endif
 struct Context;
 
-struct Server{
+struct MariadbServer{
     MYSQL *server = nullptr;
     Context *cxt = nullptr;
     bool status = false;
@@ -20,5 +20,5 @@ struct Server{
     );
     void exec(const char* q);
     void close();
-    ~Server();
+    ~MariadbServer();
 };

server/monetdb_conn.cpp

@@ -71,16 +71,17 @@ namespace types{
     };
 }
 
-Server::Server(Context* cxt){
+MonetdbServer::MonetdbServer(Context* cxt) {
+    this->DataSourceType = BACKEND_MonetDB;
     if (cxt){
         connect(cxt);
     } 
 }
 
-void Server::connect(Context *cxt){
+void MonetdbServer::connect(Context *cxt){
     auto server = static_cast<monetdbe_database*>(this->server);
     if (cxt){
-        cxt->alt_server = this;
+        cxt->alt_server[DataSourceType] = this;
         this->cxt = cxt;
     }
     else{
@@ -89,7 +90,7 @@ void Server::connect(Context *cxt){
     }
 
     if (server){
-        printf("Error: Server %p already connected. Restart? (Y/n). \n", server);
+        printf("Error: MonetdbServer %p already connected. Restart? (Y/n). \n", server);
         char c[50];
         std::cin.getline(c, 49);
         for(int i = 0; i < 50; ++i) {
@@ -122,7 +123,7 @@ void Server::connect(Context *cxt){
     }
 }
 
-void Server::exec(const char* q){
+void MonetdbServer::exec(const char* q){
     auto server = static_cast<monetdbe_database*>(this->server);
     auto _res = static_cast<monetdbe_result*>(this->res);
     monetdbe_cnt _cnt = 0;
@@ -137,7 +138,7 @@ void Server::exec(const char* q){
     }
 }
 
-bool Server::haserror(){
+bool MonetdbServer::haserror(){
     if (last_error){
         puts(last_error);
         last_error = nullptr;
@@ -149,7 +150,7 @@ bool Server::haserror(){
 }
 
 
-void Server::print_results(const char* sep, const char* end){
+void MonetdbServer::print_results(const char* sep, const char* end){
 
     if (!haserror()){
         auto _res = static_cast<monetdbe_result*> (res);
@@ -190,7 +191,7 @@ void Server::print_results(const char* sep, const char* end){
     }
 }
 
-void Server::close(){
+void MonetdbServer::close(){
     if(this->server){
         auto server = static_cast<monetdbe_database*>(this->server);
         monetdbe_close(*server);
@@ -199,7 +200,7 @@ void Server::close(){
     }
 }
 
-void* Server::getCol(int col_idx){
+void* MonetdbServer::getCol(int col_idx, int){
     if(res){
         auto _res = static_cast<monetdbe_result*>(this->res);
         auto err_msg = monetdbe_result_fetch(_res, 
@@ -224,7 +225,7 @@ void* Server::getCol(int col_idx){
 
 #define AQ_MONETDB_FETCH(X) case monetdbe_##X: \
     return (long long)((X *)(_ret_col->data))[0]; 
-long long Server::getFirstElement() {
+long long MonetdbServer::getFirstElement() {
     if(!this->haserror() && res) {
         auto _res = static_cast<monetdbe_result*>(this->res);
         auto err_msg = monetdbe_result_fetch(_res, 
@@ -266,11 +267,11 @@ long long Server::getFirstElement() {
     return 0;
 }
 
-Server::~Server(){
+MonetdbServer::~MonetdbServer(){
     close();
 }
 
-bool Server::havehge() {
+bool MonetdbServer::havehge() {
 #if defined(_MONETDBE_LIB_) and defined(HAVE_HGE)
     // puts("true");
     return HAVE_HGE;
@@ -299,7 +300,7 @@ constexpr prt_fn_t monetdbe_prtfns[] = {
 constexpr uint32_t output_buffer_size = 65536;
 void print_monetdb_results(void* _srv, const char* sep = " ", const char* end = "\n", 
     uint32_t limit = std::numeric_limits<uint32_t>::max()) {
-    auto srv = static_cast<Server *>(_srv);
+    auto srv = static_cast<MonetdbServer *>(_srv);
     if (!srv->haserror() && srv->cnt && limit) {
         char buffer[output_buffer_size];
         auto _res = static_cast<monetdbe_result*> (srv->res);
@@ -360,7 +361,7 @@ cleanup:
 
 
 int ExecuteStoredProcedureEx(const StoredProcedure *p, Context* cxt){
-    auto server = static_cast<Server*>(cxt->alt_server);
+    auto server = static_cast<MonetdbServer*>(cxt->alt_server[BACKEND_MonetDB]);
     int ret = 0;
     bool return_from_procedure = false;
     void* handle = nullptr;

server/monetdb_conn.h

@@ -1,31 +1,19 @@
 #ifndef __MONETDB_CONN_H__
 #define __MONETDB_CONN_H__
+#include "DataSource_conn.h"
 
-struct Context;
-
-struct Server{
-    void *server = nullptr;
-    Context *cxt = nullptr;
-    bool status = false;
-    char* query = nullptr;
-    int type = 1;
-
-    void* res = nullptr;
-    void* ret_col = nullptr;
-    long long cnt = 0;
-    char* last_error = nullptr;
-    
-    explicit Server(Context* cxt = nullptr);
-    void connect(Context* cxt);
-    void exec(const char* q);
-    void *getCol(int col_idx);
+struct MonetdbServer : DataSource {
+    explicit MonetdbServer(Context* cxt); 
+    void connect(Context* cxt) override;
+    void exec(const char* q) override;
+    void *getCol(int col_idx, int) override;
     long long getFirstElement();
-    void close();
-    bool haserror();
+    void close() override;
+    bool haserror() override;
     static bool havehge();
     void print_results(const char* sep = " ", const char* end = "\n");
     friend void print_monetdb_results(void* _srv, const char* sep, const char* end, int limit);
-    ~Server();
+    ~MonetdbServer() override;
 };
 
 struct monetdbe_table_data{

server/server.cpp

@@ -7,6 +7,16 @@
 
 #include "libaquery.h"
 #include "monetdb_conn.h"
+#include "duckdb_conn.h"
+
+constexpr  create_server_t get_server[] = {
+    CreateNULLServer, 
+    [](Context* cxt) -> void*{ return new MonetdbServer(cxt); }, 
+    CreateNULLServer, 
+    [](Context* cxt) -> void*{ return new DuckdbServer(cxt); }, 
+    CreateNULLServer, 
+};
+
 #pragma region misc
 #ifdef THREADING
 #include "threading.h"
@@ -89,7 +99,7 @@ extern "C" int __DLLEXPORT__ binary_info() {
 __AQEXPORT__(bool) 
 have_hge() {
 #if defined(__MONETDB_CONN_H__)
-    return Server::havehge();
+    return MonetdbServer::havehge();
 #else
     return false;
 #endif
@@ -205,13 +215,20 @@ int dll_main(int argc, char** argv, Context* cxt){
     cxt->cfg = cfg;
     cxt->n_buffers = cfg->n_buffers;
     cxt->sz_bufs = buf_szs;
-    if (cfg->backend_type == BACKEND_MonetDB && cxt->alt_server == nullptr)
-    {
-        auto alt_server = new Server(cxt);
-        alt_server->exec("SELECT '**** WELCOME TO AQUERY++! ****';");
-        puts(*(const char**)(alt_server->getCol(0)));
-        cxt->alt_server = alt_server;
+
+    
+    const auto& update_backend = [&cxt, &cfg](){
+        auto& curr_server = cxt->alt_server[cfg->backend_type];
+        if (curr_server == nullptr) {
+            curr_server = get_server[cfg->backend_type](cxt);
+            cxt->alt_server[cfg->backend_type] = curr_server;
+            static_cast<DataSource*>(curr_server)->exec("SELECT '**** WELCOME TO AQUERY++! ****';");
+            puts(*(const char**)(static_cast<DataSource*>(curr_server)->getCol(0, types::Types<const char*>::getType())));
         }
+        cxt->curr_server = curr_server;
+    };
+    update_backend();
+
     while(cfg->running){
         ENGINE_ACQUIRE();
         if (cfg->new_query) {
@@ -221,10 +238,11 @@ start:
 
             void *handle = nullptr;
             void *user_module_handle = nullptr;
-            if (cfg->backend_type == BACKEND_MonetDB){
-                if (cxt->alt_server == nullptr)
-                    cxt->alt_server = new Server(cxt);
-                Server* server = reinterpret_cast<Server*>(cxt->alt_server);
+            if (cfg->backend_type == BACKEND_MonetDB||
+                cfg->backend_type == BACKEND_DuckDB
+            ) {
+                update_backend();
+                auto server = reinterpret_cast<DataSource*>(cxt->curr_server);
                 if(n_recv > 0){
                     if (cfg->backend_type == BACKEND_AQuery || cfg->has_dll) {
                         const char* proc_name = "./dll.so";

server/table_ext_monetdb.hpp

@@ -67,7 +67,7 @@ void TableInfo<Ts ...>::monetdb_append_table(void* srv, const char* alt_name) {
 	auto last_comma = create_table_str.find_last_of(',');
 	if (last_comma != static_cast<decltype(last_comma)>(-1)) {
 		create_table_str[last_comma] = ')';
-		Server* server = (Server*)srv;
+		MonetdbServer* server = (MonetdbServer*)srv;
 		// puts("create table...");
 		// puts(create_table_str.c_str());
 		server->exec(create_table_str.c_str());

server/vector_type.hpp

@@ -169,7 +169,7 @@ public:
 			return distinct_copy();
 	}
 	// TODO: think of situations where this is a temp!! (copy on write!!!)
-	template <bool _grow = true>
+	template <bool _grow = true, bool _resize = false>
 	inline void grow(uint32_t sz = 0) {
 		if constexpr (_grow)
 			sz = this->size;
@@ -192,6 +192,8 @@ public:
 				n_container = (_Ty*)malloc(new_capacity * sizeof(_Ty));
 				memcpy(n_container, container, sizeof(_Ty) * size);
 			}
+			if constexpr(_resize) 
+				size = sz;
 			memset(n_container + size, 0, sizeof(_Ty) * (new_capacity - size));
 			// if (capacity)
 			// 	free(container);
@@ -200,8 +202,7 @@ public:
 		}
 	}
 	inline void resize(const uint32_t sz){
-		size = sz;
-		grow<false>(sz);
+		grow<false, true>(sz);
 	}
 	inline void reserve(const uint32_t sz){
 		grow<false>(sz);