Fix caching of foreign-key-checking queries so that when a replan is needed,

we regenerate the SQL query text not merely the plan derived from it.  This
is needed to handle contingencies such as renaming of a table or column
used in an FK.  Pre-8.3, such cases worked despite the lack of replanning
(because the cached plan needn't actually change), so this is a regression.
Per bug #4417 from Benjamin Bihler.

diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 748483cad09798e2214256ca0b80705ebde940a6..c22992128d2ddcb84f31a80db658c25baf999385 100644 (file)
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -1367,6 +1367,36 @@ SPI_is_cursor_plan(SPIPlanPtr plan)
        return false;
 }
 
+/*
+ * SPI_plan_is_valid --- test whether a SPI plan is currently valid
+ * (that is, not marked as being in need of revalidation).
+ *
+ * See notes for CachedPlanIsValid before using this.
+ */
+bool
+SPI_plan_is_valid(SPIPlanPtr plan)
+{
+       Assert(plan->magic == _SPI_PLAN_MAGIC);
+       if (plan->saved)
+       {
+               ListCell   *lc;
+
+               foreach(lc, plan->plancache_list)
+               {
+                       CachedPlanSource *plansource = (CachedPlanSource *) lfirst(lc);
+
+                       if (!CachedPlanIsValid(plansource))
+                               return false;
+               }
+               return true;
+       }
+       else
+       {
+               /* An unsaved plan is assumed valid for its (short) lifetime */
+               return true;
+       }
+}
+
 /*
  * SPI_result_code_string --- convert any SPI return code to a string
  *

diff --git a/src/backend/utils/adt/ri_triggers.c b/src/backend/utils/adt/ri_triggers.c
index 83170eca65cac0647488df1bf9bbdb66c1cdd664..9cab2675a42c5613477ae6529691fc83bf42b545 100644 (file)
--- a/src/backend/utils/adt/ri_triggers.c
+++ b/src/backend/utils/adt/ri_triggers.c
@@ -3615,6 +3615,7 @@ static SPIPlanPtr
 ri_FetchPreparedPlan(RI_QueryKey *key)
 {
        RI_QueryHashEntry *entry;
+       SPIPlanPtr              plan;
 
        /*
         * On the first call initialize the hashtable
@@ -3630,7 +3631,30 @@ ri_FetchPreparedPlan(RI_QueryKey *key)
                                                                                          HASH_FIND, NULL);
        if (entry == NULL)
                return NULL;
-       return entry->plan;
+
+       /*
+        * Check whether the plan is still valid.  If it isn't, we don't want
+        * to simply rely on plancache.c to regenerate it; rather we should
+        * start from scratch and rebuild the query text too.  This is to cover
+        * cases such as table/column renames.  We depend on the plancache
+        * machinery to detect possible invalidations, though.
+        *
+        * CAUTION: this check is only trustworthy if the caller has already
+        * locked both FK and PK rels.
+        */
+       plan = entry->plan;
+       if (plan && SPI_plan_is_valid(plan))
+               return plan;
+
+       /*
+        * Otherwise we might as well flush the cached plan now, to free a
+        * little memory space before we make a new one.
+        */
+       entry->plan = NULL;
+       if (plan)
+               SPI_freeplan(plan);
+
+       return NULL;
 }
 
 
@@ -3653,11 +3677,13 @@ ri_HashPreparedPlan(RI_QueryKey *key, SPIPlanPtr plan)
                ri_InitHashTables();
 
        /*
-        * Add the new plan.
+        * Add the new plan.  We might be overwriting an entry previously
+        * found invalid by ri_FetchPreparedPlan.
         */
        entry = (RI_QueryHashEntry *) hash_search(ri_query_cache,
                                                                                          (void *) key,
                                                                                          HASH_ENTER, &found);
+       Assert(!found || entry->plan == NULL);
        entry->plan = plan;
 }
 

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 3935a255b2b79277aa8e66f865dfebb0ffcdf60c..c8cad02a0993af439bca2073b976a25f13c70fc0 100644 (file)
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -571,6 +571,44 @@ ReleaseCachedPlan(CachedPlan *plan, bool useResOwner)
                MemoryContextDelete(plan->context);
 }
 
+/*
+ * CachedPlanIsValid: test whether the plan within a CachedPlanSource is
+ * currently valid (that is, not marked as being in need of revalidation).
+ *
+ * This result is only trustworthy (ie, free from race conditions) if
+ * the caller has acquired locks on all the relations used in the plan.
+ */
+bool
+CachedPlanIsValid(CachedPlanSource *plansource)
+{
+       CachedPlan *plan;
+
+       /* Validity check that we were given a CachedPlanSource */
+       Assert(list_member_ptr(cached_plans_list, plansource));
+
+       plan = plansource->plan;
+       if (plan && !plan->dead)
+       {
+               /*
+                * Plan must have positive refcount because it is referenced by
+                * plansource; so no need to fear it disappears under us here.
+                */
+               Assert(plan->refcount > 0);
+
+               /*
+                * Although we don't want to acquire locks here, it still seems
+                * useful to check for expiration of a transient plan.
+                */
+               if (TransactionIdIsValid(plan->saved_xmin) &&
+                       !TransactionIdEquals(plan->saved_xmin, TransactionXmin))
+                       plan->dead = true;
+               else
+                       return true;
+       }
+
+       return false;
+}
+
 /*
  * AcquireExecutorLocks: acquire locks needed for execution of a fully-planned
  * cached plan; or release them if acquire is false.

diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index 883dc66462bd89a305482042b3ff36d4df5ede1b..7a3824beda2f0329aea015be99a177b967dde212 100644 (file)
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -118,6 +118,7 @@ extern int  SPI_freeplan(SPIPlanPtr plan);
 extern Oid     SPI_getargtypeid(SPIPlanPtr plan, int argIndex);
 extern int     SPI_getargcount(SPIPlanPtr plan);
 extern bool SPI_is_cursor_plan(SPIPlanPtr plan);
+extern bool SPI_plan_is_valid(SPIPlanPtr plan);
 extern const char *SPI_result_code_string(int code);
 
 extern HeapTuple SPI_copytuple(HeapTuple tuple);

diff --git a/src/include/utils/plancache.h b/src/include/utils/plancache.h
index eeffd5f68d8a94d50c81b74f176654e582c93228..f266fbde6065ef1d3fbcaea30b6c0eacb785ba05 100644 (file)
--- a/src/include/utils/plancache.h
+++ b/src/include/utils/plancache.h
@@ -109,6 +109,7 @@ extern void DropCachedPlan(CachedPlanSource *plansource);
 extern CachedPlan *RevalidateCachedPlan(CachedPlanSource *plansource,
                                         bool useResOwner);
 extern void ReleaseCachedPlan(CachedPlan *plan, bool useResOwner);
+extern bool CachedPlanIsValid(CachedPlanSource *plansource);
 extern TupleDesc PlanCacheComputeResultDesc(List *stmt_list);
 
 extern void ResetPlanCache(void);