Обсуждение: Mysteriously lost values in nodes
[Please CC any replies, thanks] I added a field to each of Var, Const, FuncExpr and OpExpr which is set during parse_expr. But somewhere between the parsing and execution the values of these fields get reset back to NULL. But only for FuncExpr and OpExpr, for Var and Const it all works as expected. I've traced with the debugger and confirmed that the field is set but that it's copied somewhere before execution and that copy didn't copy this field. The copyFuncExpr worked, it's just that another place did a copy some other way. grep reveals several places where new nodes are created but rather than just changing them all, is there a particular phase where these changes are made that I should be looking at? Thanks in advance, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
On Tue, Sep 06, 2005 at 06:06:49PM +0200, Martijn van Oosterhout wrote: > [Please CC any replies, thanks] > > I added a field to each of Var, Const, FuncExpr and OpExpr which is set > during parse_expr. But somewhere between the parsing and execution the > values of these fields get reset back to NULL. But only for FuncExpr > and OpExpr, for Var and Const it all works as expected. Did you change the functions in src/backend/nodes/*funcs.c ? Nodes are copied using those. Any time you change the definition of the node, you need to change its equalfunc, copyfunc, outfunc, and readfunc, where applicable. -- Alvaro Herrera -- Valdivia, Chile Architect, www.EnterpriseDB.com "Pensar que el espectro que vemos es ilusorio no lo despoja de espanto, sólo le suma el nuevo terror de la locura" (Perelandra, CSLewis)
Martijn van Oosterhout <kleptog@svana.org> writes:
> grep reveals several places where new nodes are created but rather than
> just changing them all, is there a particular phase where these changes
> are made that I should be looking at?
Grepping for "makeNode(OpExpr)" might help you. Offhand I'd finger
eval_const_expressions as the likely culprit. clauses.c has some other
code you'd better look at too.
Personally, when I want to add a field to a node, I grep for every
reference to one or two of the existing fields to make sure I've found
all the places I need to touch.
regards, tom lane
On Tue, Sep 06, 2005 at 01:51:25PM -0400, Tom Lane wrote: > Grepping for "makeNode(OpExpr)" might help you. Offhand I'd finger > eval_const_expressions as the likely culprit. clauses.c has some other > code you'd better look at too. Yeah, eval_const_expressions was the culprit in this case, though I think operators might have some more. > Personally, when I want to add a field to a node, I grep for every > reference to one or two of the existing fields to make sure I've found > all the places I need to touch. So there's no shortcut, I'll remember that :) Thanks for the help, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.