Some infrastructure changes for the upcoming auto-explain contrib module:

* Refactor explain.c slightly to export a convenient-to-use subroutine
for printing EXPLAIN results.

* Provide hooks for plugins to get control at ExecutorStart and ExecutorEnd
as well as ExecutorRun.

* Add some minimal support for tracking the total runtime of ExecutorRun.
This code won't actually do anything unless a plugin prods it to.

* Change the API of the DefineCustomXXXVariable functions to allow nonzero
"flags" to be specified for a custom GUC variable.  While at it, also make
the "bootstrap" default value for custom GUCs be explicitly specified as a
parameter to these functions.  This is to eliminate confusion over where the
default comes from, as has been expressed in the past by some users of the
custom-variable facility.

* Refactor GUC code a bit to ensure that a custom variable gets initialized to
something valid (like its default value) even if the placeholder value was
invalid.

1 files changed, 32 insertions, 14 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 300dc5f3fa4..e5f1b313076 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.180 2008/10/06 20:29:38 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.181 2008/11/19 01:10:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -224,7 +224,6 @@ ExplainOnePlan(PlannedStmt *plannedstmt, ParamListInfo params,
 	QueryDesc  *queryDesc;
 	instr_time	starttime;
 	double		totaltime = 0;
-	ExplainState *es;
 	StringInfoData buf;
 	int			eflags;
 
@@ -265,17 +264,9 @@ ExplainOnePlan(PlannedStmt *plannedstmt, ParamListInfo params,
 		totaltime += elapsed_time(&starttime);
 	}
 
-	es = (ExplainState *) palloc0(sizeof(ExplainState));
-
-	es->printTList = stmt->verbose;
-	es->printAnalyze = stmt->analyze;
-	es->pstmt = queryDesc->plannedstmt;
-	es->rtable = queryDesc->plannedstmt->rtable;
-
+	/* Create textual dump of plan tree */
 	initStringInfo(&buf);
-	explain_outNode(&buf,
-					queryDesc->plannedstmt->planTree, queryDesc->planstate,
-					NULL, 0, es);
+	ExplainPrintPlan(&buf, queryDesc, stmt->analyze, stmt->verbose);
 
 	/*
 	 * If we ran the command, run any AFTER triggers it queued.  (Note this
@@ -290,7 +281,7 @@ ExplainOnePlan(PlannedStmt *plannedstmt, ParamListInfo params,
 	}
 
 	/* Print info about runtime of triggers */
-	if (es->printAnalyze)
+	if (stmt->analyze)
 	{
 		ResultRelInfo *rInfo;
 		bool		show_relname;
@@ -335,7 +326,34 @@ ExplainOnePlan(PlannedStmt *plannedstmt, ParamListInfo params,
 	do_text_output_multiline(tstate, buf.data);
 
 	pfree(buf.data);
-	pfree(es);
+}
+
+/*
+ * ExplainPrintPlan -
+ *	  convert a QueryDesc's plan tree to text and append it to 'str'
+ *
+ * 'analyze' means to include runtime instrumentation results
+ * 'verbose' means a verbose printout (currently, it shows targetlists)
+ *
+ * NB: will not work on utility statements
+ */
+void
+ExplainPrintPlan(StringInfo str, QueryDesc *queryDesc,
+				 bool analyze, bool verbose)
+{
+	ExplainState	es;
+
+	Assert(queryDesc->plannedstmt != NULL);
+
+	memset(&es, 0, sizeof(es));
+	es.printTList = verbose;
+	es.printAnalyze = analyze;
+	es.pstmt = queryDesc->plannedstmt;
+	es.rtable = queryDesc->plannedstmt->rtable;
+
+	explain_outNode(str,
+					queryDesc->plannedstmt->planTree, queryDesc->planstate,
+					NULL, 0, &es);
 }
 
 /*