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 2a07be49f8e3d8511f4c083a3aefe6cdaeda9a78..9fa0097a936a8df076ceebf601893424ee48f641 100644 (file)
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/access/common/heaptuple.c,v 1.51 1999/05/25 16:06:35 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/access/common/heaptuple.c,v 1.52 1999/06/12 14:05:36 momjian Exp $
  *
  * NOTES
  *   The old interface functions have been converted to macros
@@ -27,6 +27,11 @@
 #include 
 #include 
 
+#ifdef FREE_TUPLE_MEMORY
+#include 
+#include 
+#endif
+
 #ifndef HAVE_MEMMOVE
 #include 
 #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 
+#include 
+#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 d4cc93482f867c866ba43ab8bbe12b612303d9a7..d5296ae0f609de86e64dfc2aaa66657b560b137a 100644 (file)
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.19 1999/05/25 16:12:55 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.20 1999/06/12 14:05:39 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -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 9d2677c4548a91b06a774851b3c151b1671fbfee..390ee2116d5cedd2ad3541113f09ff479359ccd6 100644 (file)
--- a/src/include/utils/portal.h
+++ b/src/include/utils/portal.h
@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: portal.h,v 1.13 1999/05/25 16:14:57 momjian Exp $
+ * $Id: portal.h,v 1.14 1999/06/12 14:05:40 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -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:
  */