I don't like last minute patches before the final freeze, but I believe that

this one could be useful for people experiencing out-of-memory crashes while
executing queries which retrieve or use a very large number of tuples.

The problem happens when storage is allocated for functions results used in
a large query, for example:

  select upper(name) from big_table;
  select big_table.array[1] from big_table;
  select count(upper(name)) from big_table;

This patch is a dirty hack that fixes the out-of-memory problem for the most
common cases, like the above ones. It is not the final solution for the
problem but it can work for some people, so I'm posting it.

The patch should be safe because all changes are under #ifdef. Furthermore
the feature can be enabled or disabled at runtime by the `free_tuple_memory'
options in the pg_options file. The option is disabled by default and must
be explicitly enabled at runtime to have any effect.

To enable the patch add the follwing line to Makefile.custom:

CUSTOM_COPT += -DFREE_TUPLE_MEMORY

To enable the option at runtime add the following line to pg_option:

free_tuple_memory=1

Massimo

diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index b20ad6dc5cfd7c9f7997b564c8897f458610e163..1a27b8625ebe005e10590bd86dec0755a7b5816d 100644 (file)
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -27,6 +27,11 @@
 #include <storage/bufpage.h>
 #include <utils/memutils.h>
 
+#ifdef FREE_TUPLE_MEMORY
+#include <utils/portal.h>
+#include <utils/trace.h>
+#endif
+
 #ifndef HAVE_MEMMOVE
 #include <regex/utils.h>
 #else
@@ -93,6 +98,9 @@ DataFill(char *data,
        int                     i;
        int                     numberOfAttributes = tupleDesc->natts;
        Form_pg_attribute *att = tupleDesc->attrs;
+#ifdef FREE_TUPLE_MEMORY
+       bool            free_tuple_memory = pg_options[OPT_FREE_TUPLE_MEMORY];
+#endif
 
        if (bit != NULL)
        {
@@ -131,6 +139,14 @@ DataFill(char *data,
                                *infomask |= HEAP_HASVARLENA;
                                data_length = VARSIZE(DatumGetPointer(value[i]));
                                memmove(data, DatumGetPointer(value[i]), data_length);
+#ifdef FREE_TUPLE_MEMORY
+                               /* try to pfree value[i] - dz */
+                               if (free_tuple_memory &&
+                                       PortalHeapMemoryIsValid(CurrentMemoryContext,
+                                                                                       (Pointer) value[i])) {
+                                       pfree(value[i]);
+                               }
+#endif
                                break;
                        case sizeof(char):
                                *data = att[i]->attbyval ?
@@ -147,8 +163,15 @@ DataFill(char *data,
                                                                   *((int32 *) value[i]));
                                break;
                        default:
-                               memmove(data, DatumGetPointer(value[i]),
-                                               att[i]->attlen);
+                               memmove(data, DatumGetPointer(value[i]), att[i]->attlen);
+#ifdef FREE_TUPLE_MEMORY
+                               /* try to pfree value[i] - dz */
+                               if (free_tuple_memory &&
+                                       PortalHeapMemoryIsValid(CurrentMemoryContext,
+                                                                                       (Pointer) value[i])) {
+                                       pfree(value[i]);
+                               }
+#endif
                                break;
                }
                data = (char *) att_addlength((long) data, att[i]->attlen, value[i]);

diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index a47a9ad5492dee479037a80c3b5254a21c2307c2..9d0f4ea10363321bed09ac2f4a906bf166b91acd 100644 (file)
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -31,6 +31,11 @@
 #include "utils/syscache.h"
 #include "optimizer/clauses.h"
 
+#ifdef FREE_TUPLE_MEMORY
+#include <utils/portal.h>
+#include <utils/trace.h>
+#endif
+
 /*
  * AggFuncInfo -
  *       keeps the transition functions information around
@@ -113,7 +118,9 @@ ExecAgg(Agg *node)
                                isNull1 = FALSE,
                                isNull2 = FALSE;
        bool            qual_result;
-
+#ifdef FREE_TUPLE_MEMORY
+       bool            free_tuple_memory = pg_options[OPT_FREE_TUPLE_MEMORY];
+#endif
 
        /* ---------------------
         *      get state info from node
@@ -241,6 +248,10 @@ ExecAgg(Agg *node)
                for (;;)
                {
                        TupleTableSlot *outerslot;
+#ifdef FREE_TUPLE_MEMORY
+                       Oid                             valueType;
+                       bool                    isByValue = 0;
+#endif
 
                        isNull = isNull1 = isNull2 = 0;
                        outerslot = ExecProcNode(outerPlan, (Plan *) node);
@@ -293,6 +304,31 @@ ExecAgg(Agg *node)
                                        newVal = ExecEvalExpr(aggref->target, econtext,
                                                                                  &isNull, &isDone);
                                }
+#ifdef FREE_TUPLE_MEMORY
+                               if (free_tuple_memory) {
+                                       switch (nodeTag(aggref->target)) {
+                                       case T_Const:
+                                               isByValue = ((Const*) (aggref->target))->constbyval;
+                                               break;
+                                       case T_Var:
+                                               valueType = ((Var*) (aggref->target))->vartype;
+                                               isByValue = typeByVal(typeidType(valueType));
+                                               break;
+                                       case T_Array:
+                                               isByValue = ((Array*)(aggref->target))->arrayelembyval;
+                                               break;
+                                       case T_ArrayRef:
+                                               isByValue =((ArrayRef*)(aggref->target))->refelembyval;
+                                               break;
+                                       case T_Expr:
+                                               valueType = ((Expr*) (aggref->target))->typeOid;
+                                               isByValue = typeByVal(typeidType(valueType));
+                                               break;
+                                       default:
+                                               break;
+                                       }
+                               }
+#endif
 
                                if (isNull && !aggref->usenulls)
                                        continue;       /* ignore this tuple for this agg */
@@ -353,6 +389,16 @@ ExecAgg(Agg *node)
                                                                                  (FmgrValues *) args, &isNull2);
                                        Assert(!isNull2);
                                }
+
+#ifdef FREE_TUPLE_MEMORY
+                               /* try to pfree newVal if not isByValue - dz */
+                               if (free_tuple_memory && !isByValue && 
+                                       PortalHeapMemoryIsValid(CurrentMemoryContext,
+                                                                                       (Pointer) newVal))
+                               {
+                                       pfree(newVal);
+                               }
+#endif
                        }
 
                        /*

diff --git a/src/backend/utils/misc/trace.c b/src/backend/utils/misc/trace.c
index 9676ca570a0c13a77b27be7d0138ed8617fa58a7..5a18a21390061bf19d2c1074db203ee479380d30 100644 (file)
--- a/src/backend/utils/misc/trace.c
+++ b/src/backend/utils/misc/trace.c
@@ -73,6 +73,9 @@ static char *opt_names[] = {
        "syslog",                                       /* use syslog for error messages */
        "hostlookup",                           /* enable hostname lookup in ps_status */
        "showportnumber",                       /* show port number in ps_status */
+#ifdef FREE_TUPLE_MEMORY
+       "free_tuple_memory",            /* try to pfree memory for each tuple */
+#endif
 
        /* NUM_PG_OPTIONS */            /* must be the last item of enum */
 };
@@ -404,9 +407,9 @@ read_pg_options(SIGNAL_ARGS)
 }
 
 /*
- * Local variables:
- *     tab-width: 4
- *     c-indent-level: 4
- *     c-basic-offset: 4
+ * Local Variables:
+ *  tab-width: 4
+ *  c-indent-level: 4
+ *  c-basic-offset: 4
  * End:
  */

diff --git a/src/backend/utils/mmgr/portalmem.c b/src/backend/utils/mmgr/portalmem.c
index 86c4ff6a2ad0b36f55bf41709ef20c59ad438371..90d2ff7685e09c0b205d3f85b644575840d230e6 100644 (file)
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -289,6 +289,24 @@ PortalHeapMemoryFree(PortalHeapMemory this,
        }
 }
 
+#ifdef FREE_TUPLE_MEMORY
+/*
+ * PortalHeapMemoryIsValid --
+ *
+ * Check if a pointer is allocated in a memory context.
+ *
+ */
+bool
+PortalHeapMemoryIsValid(MemoryContext context, Pointer pointer)
+{
+       HeapMemoryBlock block = HEAPMEMBLOCK((PortalHeapMemory) context);
+
+       AssertState(PointerIsValid(block));
+
+       return (AllocSetContains(&block->setData, pointer));
+}
+#endif
+
 /* ----------------
  *             PortalHeapMemoryRealloc
  * ----------------

diff --git a/src/include/utils/portal.h b/src/include/utils/portal.h
index b26ddf525d74f5432ba96ecf0bfb09120f41acf8..f5ada649de7824e76fc111cd2d6a350e9cff10ff 100644 (file)
--- a/src/include/utils/portal.h
+++ b/src/include/utils/portal.h
@@ -80,6 +80,10 @@ extern void EndPortalAllocMode(void);
 extern PortalVariableMemory PortalGetVariableMemory(Portal portal);
 extern PortalHeapMemory PortalGetHeapMemory(Portal portal);
 
+#ifdef FREE_TUPLE_MEMORY
+bool   PortalHeapMemoryIsValid(MemoryContext context, Pointer pointer);
+#endif
+
 /* estimate of the maximum number of open portals a user would have,
  * used in initially sizing the PortalHashTable in     EnablePortalManager()
  */

diff --git a/src/include/utils/trace.h b/src/include/utils/trace.h
index 3174026ca5cfe32ce8c6caed21b09c561c8cb088..1affd968b7e381cc75c3ab3ff9c18ecbd73aafa9 100644 (file)
--- a/src/include/utils/trace.h
+++ b/src/include/utils/trace.h
@@ -64,6 +64,9 @@ enum pg_option_enum {
        OPT_SYSLOG,                                     /* use syslog for error messages */
        OPT_HOSTLOOKUP,                         /* enable hostname lookup in ps_status */
        OPT_SHOWPORTNUMBER,                     /* show port number in ps_status */
+#ifdef FREE_TUPLE_MEMORY
+       OPT_FREE_TUPLE_MEMORY,          /* try to pfree memory for each tuple */
+#endif
 
        NUM_PG_OPTIONS                          /* must be the last item of enum */
 };
@@ -83,9 +86,9 @@ extern int    pg_options[NUM_PG_OPTIONS];
 #endif  /* TRACE_H */
 
 /*
- * Local variables:
- *     tab-width: 4
- *     c-indent-level: 4
- *     c-basic-offset: 4
+ * Local Variables:
+ *  tab-width: 4
+ *  c-indent-level: 4
+ *  c-basic-offset: 4
  * End:
  */