Simplify code by getting rid of SPI_push, SPI_pop, SPI_restore_connection.

The idea behind SPI_push was to allow transitioning back into an
"unconnected" state when a SPI-using procedure calls unrelated code that
might or might not invoke SPI.  That sounds good, but in practice the only
thing it does for us is to catch cases where a called SPI-using function
forgets to call SPI_connect --- which is a highly improbable failure mode,
since it would be exposed immediately by direct testing of said function.
As against that, we've had multiple bugs induced by forgetting to call
SPI_push/SPI_pop around code that might invoke SPI-using functions; these
are much harder to catch and indeed have gone undetected for years in some
cases.  And we've had to band-aid around some problems of this ilk by
introducing conditional push/pop pairs in some places, which really kind
of defeats the purpose altogether; if we can't draw bright lines between
connected and unconnected code, what's the point?

Hence, get rid of SPI_push[_conditional], SPI_pop[_conditional], and the
underlying state variable _SPI_curid.  It turns out SPI_restore_connection
can go away too, which is a nice side benefit since it was never more than
a kluge.  Provide no-op macros for the deleted functions so as to avoid an
API break for external modules.

A side effect of this removal is that SPI_palloc and allied functions no
longer permit being called when unconnected; they'll throw an error
instead.  The apparent usefulness of the previous behavior was a mirage
as well, because it was depended on by only a few places (which I fixed in
preceding commits), and it posed a risk of allocations being unexpectedly
long-lived if someone forgot a SPI_push call.

Discussion: <[email protected]>

1 files changed, 7 insertions, 5 deletions

diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index 1792fb12172..76ba394a2b6 100644
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -59,6 +59,13 @@ typedef struct _SPI_plan *SPIPlanPtr;
 #define SPI_OK_UPDATE_RETURNING 13
 #define SPI_OK_REWRITTEN		14
 
+/* These used to be functions, now just no-ops for backwards compatibility */
+#define SPI_push()	((void) 0)
+#define SPI_pop()	((void) 0)
+#define SPI_push_conditional()	false
+#define SPI_pop_conditional(pushed) ((void) 0)
+#define SPI_restore_connection()	((void) 0)
+
 extern PGDLLIMPORT uint64 SPI_processed;
 extern PGDLLIMPORT Oid SPI_lastoid;
 extern PGDLLIMPORT SPITupleTable *SPI_tuptable;
@@ -66,11 +73,6 @@ extern PGDLLIMPORT int SPI_result;
 
 extern int	SPI_connect(void);
 extern int	SPI_finish(void);
-extern void SPI_push(void);
-extern void SPI_pop(void);
-extern bool SPI_push_conditional(void);
-extern void SPI_pop_conditional(bool pushed);
-extern void SPI_restore_connection(void);
 extern int	SPI_execute(const char *src, bool read_only, long tcount);
 extern int SPI_execute_plan(SPIPlanPtr plan, Datum *Values, const char *Nulls,
 				 bool read_only, long tcount);