Revert my bad decision of about a year ago to make PortalDefineQuery

responsible for copying the query string into the new Portal.  Such copying
is unnecessary in the common code path through exec_simple_query, and in
this case it can be enormously expensive because the string might contain
a large number of individual commands; we were copying the entire, long
string for each command, resulting in O(N^2) behavior for N commands.
(This is the cause of bug #4079.)  A second problem with it is that
PortalDefineQuery really can't risk error, because if it elog's before
having set up the Portal, we will leak the plancache refcount that the
caller is trying to hand off to the portal.  So go back to the design in
which the caller is responsible for making sure everything is copied into
the portal if necessary.

diff --git a/src/backend/commands/portalcmds.c b/src/backend/commands/portalcmds.c
index f7ac06566aa0f0b1088424a922c4801c5484bf99..ce038d80ae57cd1da1f8c54589365f695f5a4928 100644 (file)
--- a/src/backend/commands/portalcmds.c
+++ b/src/backend/commands/portalcmds.c
@@ -76,6 +76,9 @@ PerformCursorOpen(PlannedStmt *stmt, ParamListInfo params,
        stmt = copyObject(stmt);
        stmt->utilityStmt = NULL;       /* make it look like plain SELECT */
 
+       if (queryString)                        /* copy the source text too for safety */
+               queryString = pstrdup(queryString);
+
        PortalDefineQuery(portal,
                                          NULL,
                                          queryString,

diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index 69d3aef3d9a4397f8e68ac6ee901ba109815f830..5d53e512de13a36374302402359502c12225e5b8 100644 (file)
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -249,9 +249,13 @@ ExecuteQuery(ExecuteStmt *stmt, const char *queryString,
                plan_list = cplan->stmt_list;
        }
 
+       /*
+        * Note: we don't bother to copy the source query string into the portal.
+        * Any errors it might be useful for will already have been reported.
+        */
        PortalDefineQuery(portal,
                                          NULL,
-                                         entry->plansource->query_string,
+                                         NULL,
                                          entry->plansource->commandTag,
                                          plan_list,
                                          cplan);

diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 76769dbcbe1de5337fab0c833cdf1bd5f453d624..31820de6d862d1c741ec251808996520064e2cb5 100644 (file)
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -858,6 +858,7 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
        CachedPlanSource *plansource;
        CachedPlan *cplan;
        List       *stmt_list;
+       char       *query_string;
        ParamListInfo paramLI;
        Snapshot        snapshot;
        MemoryContext oldcontext;
@@ -908,10 +909,22 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
                portal = CreatePortal(name, false, false);
        }
 
+       /*
+        * Prepare to copy stuff into the portal's memory context.  We do all this
+        * copying first, because it could possibly fail (out-of-memory) and we
+        * don't want a failure to occur between RevalidateCachedPlan and
+        * PortalDefineQuery; that would result in leaking our plancache refcount.
+        */
+       oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
+
+       /* Copy the plan's query string, if available, into the portal */
+       query_string = plansource->query_string;
+       if (query_string)
+               query_string = pstrdup(query_string);
+
        /* If the plan has parameters, copy them into the portal */
        if (plan->nargs > 0)
        {
-               oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
                /* sizeof(ParamListInfoData) includes the first array element */
                paramLI = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
                                                                 (plan->nargs - 1) *sizeof(ParamExternData));
@@ -940,11 +953,12 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
                                                                           paramTypByVal, paramTypLen);
                        }
                }
-               MemoryContextSwitchTo(oldcontext);
        }
        else
                paramLI = NULL;
 
+       MemoryContextSwitchTo(oldcontext);
+
        if (plan->saved)
        {
                /* Replan if needed, and increment plan refcount for portal */
@@ -965,7 +979,7 @@ SPI_cursor_open(const char *name, SPIPlanPtr plan,
         */
        PortalDefineQuery(portal,
                                          NULL,         /* no statement name */
-                                         plansource->query_string,
+                                         query_string,
                                          plansource->commandTag,
                                          stmt_list,
                                          cplan);

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index a03d29a20e10cd0ec852d9c25e6b2ab402c45db7..12ebce44fd6184a01cca9a6bac0bb61ca0d504c8 100644 (file)
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -931,6 +931,11 @@ exec_simple_query(const char *query_string)
                /* Don't display the portal in pg_cursors */
                portal->visible = false;
 
+               /*
+                * We don't have to copy anything into the portal, because everything
+                * we are passsing here is in MessageContext, which will outlive the
+                * portal anyway.
+                */
                PortalDefineQuery(portal,
                                                  NULL,
                                                  query_string,
@@ -1354,8 +1359,11 @@ exec_bind_message(StringInfo input_message)
        CachedPlanSource *psrc;
        CachedPlan *cplan;
        Portal          portal;
+       char       *query_string;
+       char       *saved_stmt_name;
        ParamListInfo params;
        List       *plan_list;
+       MemoryContext oldContext;
        bool            save_log_statement_stats = log_statement_stats;
        char            msec_str[32];
 
@@ -1459,16 +1467,32 @@ exec_bind_message(StringInfo input_message)
        else
                portal = CreatePortal(portal_name, false, false);
 
+       /*
+        * Prepare to copy stuff into the portal's memory context.  We do all this
+        * copying first, because it could possibly fail (out-of-memory) and we
+        * don't want a failure to occur between RevalidateCachedPlan and
+        * PortalDefineQuery; that would result in leaking our plancache refcount.
+        */
+       oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
+
+       /* Copy the plan's query string, if available, into the portal */
+       query_string = psrc->query_string;
+       if (query_string)
+               query_string = pstrdup(query_string);
+
+       /* Likewise make a copy of the statement name, unless it's unnamed */
+       if (stmt_name[0])
+               saved_stmt_name = pstrdup(stmt_name);
+       else
+               saved_stmt_name = NULL;
+
        /*
         * Fetch parameters, if any, and store in the portal's memory context.
         */
        if (numParams > 0)
        {
-               MemoryContext oldContext;
                int                     paramno;
 
-               oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
-
                /* sizeof(ParamListInfoData) includes the first array element */
                params = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
                                                                   (numParams - 1) *sizeof(ParamExternData));
@@ -1593,12 +1617,13 @@ exec_bind_message(StringInfo input_message)
                        params->params[paramno].pflags = PARAM_FLAG_CONST;
                        params->params[paramno].ptype = ptype;
                }
-
-               MemoryContextSwitchTo(oldContext);
        }
        else
                params = NULL;
 
+       /* Done storing stuff in portal's context */
+       MemoryContextSwitchTo(oldContext);
+
        /* Get the result format codes */
        numRFormats = pq_getmsgint(input_message, 2);
        if (numRFormats > 0)
@@ -1625,7 +1650,6 @@ exec_bind_message(StringInfo input_message)
        }
        else
        {
-               MemoryContext oldContext;
                List       *query_list;
 
                /*
@@ -1663,8 +1687,8 @@ exec_bind_message(StringInfo input_message)
         * Define portal and start execution.
         */
        PortalDefineQuery(portal,
-                                         stmt_name[0] ? stmt_name : NULL,
-                                         psrc->query_string,
+                                         saved_stmt_name,
+                                         query_string,
                                          psrc->commandTag,
                                          plan_list,
                                          cplan);

diff --git a/src/backend/utils/mmgr/portalmem.c b/src/backend/utils/mmgr/portalmem.c
index b2ee8959a0de8e9172a5e54b049f0076fe8b30bc..6f5cac7f062cc79842259b5683048ce63b123492 100644 (file)
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -274,9 +274,7 @@ CreateNewPortal(void)
  *
  * Notes: commandTag shall be NULL if and only if the original query string
  * (before rewriting) was an empty string.     Also, the passed commandTag must
- * be a pointer to a constant string, since it is not copied.  However,
- * prepStmtName and sourceText, if provided, are copied into the portal's
- * heap context for safekeeping.
+ * be a pointer to a constant string, since it is not copied.
  *
  * If cplan is provided, then it is a cached plan containing the stmts,
  * and the caller must have done RevalidateCachedPlan(), causing a refcount
@@ -285,6 +283,14 @@ CreateNewPortal(void)
  * If cplan is NULL, then it is the caller's responsibility to ensure that
  * the passed plan trees have adequate lifetime.  Typically this is done by
  * copying them into the portal's heap context.
+ *
+ * The caller is also responsible for ensuring that the passed prepStmtName
+ * and sourceText (if not NULL) have adequate lifetime.
+ *
+ * NB: this function mustn't do much beyond storing the passed values; in
+ * particular don't do anything that risks elog(ERROR).  If that were to
+ * happen here before storing the cplan reference, we'd leak the plancache
+ * refcount that the caller is trying to hand off to us.
  */
 void
 PortalDefineQuery(Portal portal,
@@ -299,10 +305,8 @@ PortalDefineQuery(Portal portal,
 
        Assert(commandTag != NULL || stmts == NIL);
 
-       portal->prepStmtName = prepStmtName ?
-               MemoryContextStrdup(PortalGetHeapMemory(portal), prepStmtName) : NULL;
-       portal->sourceText = sourceText ?
-               MemoryContextStrdup(PortalGetHeapMemory(portal), sourceText) : NULL;
+       portal->prepStmtName = prepStmtName;
+       portal->sourceText = sourceText;
        portal->commandTag = commandTag;
        portal->stmts = stmts;
        portal->cplan = cplan;