Support loading of injection points

This can be used to load an injection point and prewarm the
backend-level cache before running it, to avoid issues if the point
cannot be loaded due to restrictions in the code path where it would be
run, like a critical section where no memory allocation can happen
(load_external_function() can do allocations when expanding a library
name).

Tests can use a macro called INJECTION_POINT_LOAD() to load an injection
point.  The test module injection_points gains some tests, and a SQL
function able to load an injection point.

Based on a request from Andrey Borodin, who has implemented a test for
multixacts requiring this facility.

Reviewed-by: Andrey Borodin
Discussion: https://postgr.es/m/ZkrBE1e2q2wGvsoN@paquier.xyz

1 files changed, 3 insertions, 0 deletions

diff --git a/src/include/utils/injection_point.h b/src/include/utils/injection_point.h
index a61d5d44391..bd3a62425c3 100644
--- a/src/include/utils/injection_point.h
+++ b/src/include/utils/injection_point.h
@@ -15,8 +15,10 @@
  * Injections points require --enable-injection-points.
  */
 #ifdef USE_INJECTION_POINTS
+#define INJECTION_POINT_LOAD(name) InjectionPointLoad(name)
 #define INJECTION_POINT(name) InjectionPointRun(name)
 #else
+#define INJECTION_POINT_LOAD(name) ((void) name)
 #define INJECTION_POINT(name) ((void) name)
 #endif
 
@@ -34,6 +36,7 @@ extern void InjectionPointAttach(const char *name,
 								 const char *function,
 								 const void *private_data,
 								 int private_data_size);
+extern void InjectionPointLoad(const char *name);
 extern void InjectionPointRun(const char *name);
 extern bool InjectionPointDetach(const char *name);