Add basic tuple and value fetching from queries.

Add safeties for =destroy hooks.

FossilOrigin-Name: 2fae5297a0d0598cc3580777688b4f4307de008d4f379d2fb224c8a74cb9b708

src/kuzu/tuple.nim

@@ -0,0 +1,23 @@
+# vim: set et sta sw=4 ts=4 :
+
+proc `=destroy`*( tpl: KuzuFlatTupleObj ) =
+    ## Graceful cleanup for out of scope tuples.
+    if tpl.valid:
+        kuzu_flat_tuple_destroy( addr tpl.handle )
+
+
+proc `$`*( tpl: KuzuFlatTuple ): string =
+    ## Stringify a tuple.
+    result = $kuzu_flat_tuple_to_string( addr tpl.handle )
+    result.removeSuffix( "\n" )
+
+
+proc `[]`*( tpl: KuzuFlatTuple, idx: int ): KuzuValue =
+    ## Returns a KuzuValue at the given +idx+.
+    result = new KuzuValue
+    if kuzu_flat_tuple_get_value( addr tpl.handle, idx.uint64, addr result.handle ) == KuzuSuccess:
+        result.valid = true
+    else:
+        raise newException( KuzuIndexException,
+            &"Unable to fetch tuple value at idx {idx}. ({tpl.num_columns} column(s).)" )
+