Re: [GENERAL] DECLARE CURSOR

Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> Let's just fix it and roll an RC2 with the fix. If not, we can just fix
> it in 7.3.1 but I see little problem in rolling an RC2.

Here is the patch I am testing (in current sources; I don't think it
needs any adjustments for REL7_3, but haven't tried to apply it yet).
Basically it moves the test that was originally done in parse/analyze.c
into the execution-time setup of a cursor, and enlarges the test to
understand about autocommit-off and inside-a-function exceptions.
Anyone see a problem?

regards, tom lane

*** src/backend/access/transam/xact.c.orig Wed Nov 13 10:51:46 2002
--- src/backend/access/transam/xact.c Sun Nov 17 19:10:20 2002
***************
*** 1488,1493 ****
--- 1488,1537 ----
}
}

+ /* --------------------------------
+ * RequireTransactionChain
+ *
+ * This routine is to be called by statements that must run inside
+ * a transaction block, because they have no effects that persist past
+ * transaction end (and so calling them outside a transaction block
+ * is presumably an error). DECLARE CURSOR is an example.
+ *
+ * If we appear to be running inside a user-defined function, we do not
+ * issue an error, since the function could issue more commands that make
+ * use of the current statement's results. Thus this is an inverse for
+ * PreventTransactionChain.
+ *
+ * stmtNode: pointer to parameter block for statement; this is used in
+ * a very klugy way to determine whether we are inside a function.
+ * stmtType: statement type name for error messages.
+ * --------------------------------
+ */
+ void
+ RequireTransactionChain(void *stmtNode, const char *stmtType)
+ {
+ /*
+ * xact block already started?
+ */
+ if (IsTransactionBlock())
+ return;
+ /*
+ * Are we inside a function call? If the statement's parameter block
+ * was allocated in QueryContext, assume it is an interactive command.
+ * Otherwise assume it is coming from a function.
+ */
+ if (!MemoryContextContains(QueryContext, stmtNode))
+ return;
+ /*
+ * If we are in autocommit-off mode then it's okay, because this
+ * statement will itself start a transaction block.
+ */
+ if (!autocommit && !suppressChain)
+ return;
+ /* translator: %s represents an SQL statement name */
+ elog(ERROR, "%s may only be used in begin/end transaction blocks",
+ stmtType);
+ }
+

/* ----------------------------------------------------------------
* transaction block support
*** /home/postgres/pgsql/src/backend/tcop/pquery.c.orig Wed Sep 4 17:30:43 2002
--- /home/postgres/pgsql/src/backend/tcop/pquery.c Sun Nov 17 19:10:26 2002
***************
*** 161,166 ****
--- 161,168 ----
/* If binary portal, switch to alternate output format */
if (dest == Remote && parsetree->isBinary)
dest = RemoteInternal;
+ /* Check for invalid context (must be in transaction block) */
+ RequireTransactionChain((void *) parsetree, "DECLARE CURSOR");
}
else if (parsetree->into != NULL)
{
*** /home/postgres/pgsql/src/include/access/xact.h.orig Wed Nov 13 10:52:07 2002
--- /home/postgres/pgsql/src/include/access/xact.h Sun Nov 17 19:10:13 2002
***************
*** 115,120 ****
--- 115,121 ----
extern void UserAbortTransactionBlock(void);
extern void AbortOutOfAnyTransaction(void);
extern void PreventTransactionChain(void *stmtNode, const char *stmtType);
+ extern void RequireTransactionChain(void *stmtNode, const char *stmtType);

extern void RecordTransactionCommit(void);