Insert conditional SPI_push/SPI_pop calls into InputFunctionCall,

OutputFunctionCall, and friends.  This allows SPI-using functions to invoke
datatype I/O without concern for the possibility that a SPI-using function
will be called (which could be either the I/O function itself, or a function
used in a domain check constraint).  It's a tad ugly, but not nearly as ugly
as what'd be needed to make this work via retail insertion of push/pop
operations in all the PLs.

This reverts my patch of 2007-01-30 that inserted some retail SPI_push/pop
calls into plpgsql; that approach only fixed plpgsql, and not any other PLs.
But the other PLs have the issue too, as illustrated by a recent gripe from
Christian Schröder.

Back-patch to 8.2, which is as far back as this solution will work.  It's
also as far back as we need to worry about the domain-constraint case, since
earlier versions did not attempt to check domain constraints within datatype
input.  I'm not aware of any old I/O functions that use SPI themselves, so
this should be sufficient for a back-patch.

1 files changed, 26 insertions, 1 deletions

diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 5391dcb6e9b..aa562c2ea9a 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.205 2009/01/07 13:44:36 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/spi.c,v 1.206 2009/01/07 20:38:56 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -304,6 +304,31 @@ SPI_pop(void)
 	_SPI_curid--;
 }
 
+/* Conditional push: push only if we're inside a SPI procedure */
+bool
+SPI_push_conditional(void)
+{
+	bool	pushed = (_SPI_curid != _SPI_connected);
+
+	if (pushed)
+	{
+		_SPI_curid++;
+		/* We should now be in a state where SPI_connect would succeed */
+		Assert(_SPI_curid == _SPI_connected);
+	}
+	return pushed;
+}
+
+/* Conditional pop: pop only if SPI_push_conditional pushed */
+void
+SPI_pop_conditional(bool pushed)
+{
+	/* We should be in a state where SPI_connect would succeed */
+	Assert(_SPI_curid == _SPI_connected);
+	if (pushed)
+		_SPI_curid--;
+}
+
 /* Restore state of SPI stack after aborting a subtransaction */
 void
 SPI_restore_connection(void)