On Thu, 2004-11-18 at 13:18 +0000, Matt wrote:
> I got extremely frustrated with having to create a temp table every time
> I wanted to access an arbitrary column from a record plpgsql.
FYI, one thing I want to implement is an EVALUATE statement in plpgsql
(analogous to eval() in Perl, for example). If I understand your use
case, I think this will help somewhat, although of course it is still
clumsier than direct syntactic support.
> Warning: I Am Not a C Programmer! I haven't even written a hello world
> in C before, and I knew nothing about Flex before yesterday. It was fun
> figuring stuff out, I'm amazed it mostly works, but I'm really hoping
> someone can point out my mistakes.
An impressive first hack! :)
> Enable users to access fields in record variables using the following
> syntax like the following [...]
> rec.(1)
Looks good.
> rec.('foo')
I don't like this: it implicitly coerces a string literal into an
identifier (i.e. a column name). Treating data as code can be useful,
but I think we need to make it more obvious to the user. I think a
proper EVALUATE statement might be a better solution.
> 5. Because of the way the expression is parsed (looking for closing
> parenth), this will choke if you try and put a function in there. Would
> it be better to use curly braces '{expr}' or another character to mark
> the expression?
How much thought went into choosing parentheses? (i.e. is a similar
syntax used in the procedural languages in other DBs?)
In any case, I don't think switching switching to braces is the right
solution to the lexing problem. I _believe_ the patch is OK as is --
plpgsql_read_expression() keeps track of parenthesis nesting so it
should be able to figure out when it sees an "unmatched" parenthesis
(indicating the end of the expression).
BTW, attached is a trivial incremental patch that fixes a few compile
warnings (which are indicative of actual problems) in your patch.
-Neil
diff -u src/pl/plpgsql/src/pl_exec.c src/pl/plpgsql/src/pl_exec.c
--- src/pl/plpgsql/src/pl_exec.c
+++ src/pl/plpgsql/src/pl_exec.c
@@ -2989,11 +2989,11 @@
{
Datum exprdatum;
Oid exprtype;
- bool *exprisnull;
+ bool exprisnull;
/* Evaluate expression */
exprdatum = exec_eval_expr(estate, recfield->expr,
- exprisnull, &exprtype);
+ &exprisnull, &exprtype);
/* If we've got an integer, it's a field number, otherwise
* it's a fieldname
@@ -3002,7 +3002,7 @@
exprdatum = exec_simple_cast_value(exprdatum,
exprtype,
INT4OID, -1,
- exprisnull);
+ &exprisnull);
fno = DatumGetInt32(exprdatum);
}
else {
@@ -3357,11 +3357,11 @@
{
Datum exprdatum;
Oid exprtype;
- bool *exprisnull;
+ bool exprisnull;
/* Evaluate expression */
exprdatum = exec_eval_expr(estate, recfield->expr,
- exprisnull, &exprtype);
+ &exprisnull, &exprtype);
/* If we've got an integer, it's a field number, otherwise
@@ -3371,7 +3371,7 @@
exprdatum = exec_simple_cast_value(exprdatum,
exprtype,
INT4OID, -1,
- exprisnull);
+ &exprisnull);
fno = DatumGetInt32(exprdatum);
}
else {
---------------------------(end of broadcast)---------------------------
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