New QUERY_LIMIT set command.

doc/src/sgml/ref/set.sgml

@@ -415,6 +415,44 @@ Equivalent to specifying <command>SET R_PLANS=Off</command>.
                 The frontend may be initialized by setting the PGRPLANS
                 environment variable.
 
+<varlistentry>
+<term>
+QUERY_LIMIT
+</term>
+<listitem>
+<para>
+Sets the number of rows returned by a query.
+
+<variablelist>
+<varlistentry>
+<term>
+Value
+</term>
+<listitem>
+<para>
+Maximum number of rows to return for a query.  The default is unlimited.
+<varlistentry>
+<term>
+<replaceable class="parameter">#</replaceable>
+</term>
+<listitem>
+<para>
+Sets the maximum number of rows returned by a
+query to <replaceable class="parameter">#</replaceable>.
+<varlistentry>
+<term>
+DEFAULT
+</term>
+<listitem>
+<para>
+Sets the number of rows returned by a query to unlimited.
+</varlistentry>
+
+<para>
+                By default, there is no limit to the number of rows
+		returned by a query.
+</variablelist>
+
 </VARLISTENTRY>
 </VARIABLELIST>
 </REFSECT2>

src/backend/commands/variable.c

@@ -2,7 +2,7 @@
  * Routines for handling of 'SET var TO',
  *	'SHOW var' and 'RESET var' statements.
  *
- * $Id: variable.c,v 1.15 1998/10/08 23:50:28 tgl Exp $
+ * $Id: variable.c,v 1.16 1998/10/14 05:09:58 momjian Exp $
  *
  */
 
@@ -18,6 +18,10 @@
 #ifdef MULTIBYTE
 #include "mb/pg_wchar.h"
 #endif
+#ifdef QUERY_LIMIT
+#include "executor/executor.h"
+#include "executor/execdefs.h"
+#endif
 
 static bool show_date(void);
 static bool reset_date(void);
@@ -40,6 +44,11 @@ static bool parse_geqo(const char *);
 static bool show_ksqo(void);
 static bool reset_ksqo(void);
 static bool parse_ksqo(const char *);
+#ifdef QUERY_LIMIT
+static bool show_query_limit(void);
+static bool reset_query_limit(void);
+static bool parse_query_limit(const char *);
+#endif
 
 extern Cost _cpu_page_wight_;
 extern Cost _cpu_index_page_wight_;
@@ -48,7 +57,11 @@ extern int32 _use_geqo_rels_;
 extern bool _use_right_sided_plans_;
 extern bool _use_keyset_query_optimizer;
 
-/*-----------------------------------------------------------------------*/
+/*
+ *
+ * Get_Token
+ *
+ */
 static const char *
 get_token(char **tok, char **val, const char *str)
 {
@@ -149,7 +162,11 @@ get_token(char **tok, char **val, const char *str)
 	return str;
 }
 
-/*-----------------------------------------------------------------------*/
+/*
+ *
+ * GEQO
+ *
+ */
 static bool
 parse_geqo(const char *value)
 {
@@ -221,6 +238,11 @@ reset_geqo(void)
 	return TRUE;
 }
 
+/*
+ *
+ * R_PLANS
+ *
+ */
 static bool
 parse_r_plans(const char *value)
 {
@@ -240,7 +262,6 @@ parse_r_plans(const char *value)
 	return TRUE;
 }
 
-/*-----------------------------------------------------------------------*/
 static bool
 show_r_plans()
 {
@@ -264,7 +285,11 @@ reset_r_plans()
 	return TRUE;
 }
 
-/*-----------------------------------------------------------------------*/
+/*
+ *
+ * COST_HEAP
+ *
+ */
 static bool
 parse_cost_heap(const char *value)
 {
@@ -297,7 +322,11 @@ reset_cost_heap()
 	return TRUE;
 }
 
-/*-----------------------------------------------------------------------*/
+/*
+ *
+ * COST_INDEX
+ *
+ */
 static bool
 parse_cost_index(const char *value)
 {
@@ -330,7 +359,11 @@ reset_cost_index()
 	return TRUE;
 }
 
-/*-----------------------------------------------------------------------*/
+/*
+ *
+ * DATE_STYLE
+ *
+ */
 static bool
 parse_date(const char *value)
 {
@@ -448,6 +481,11 @@ static char *defaultTZ = NULL;
 static char TZvalue[64];
 static char tzbuf[64];
 
+/*
+ *
+ * TIMEZONE
+ *
+ */
 /* parse_timezone()
  * Handle SET TIME ZONE...
  * Try to save existing TZ environment variable for later use in RESET TIME ZONE.
@@ -545,7 +583,53 @@ reset_timezone()
 	return TRUE;
 }	/* reset_timezone() */
 
+/*
+ *
+ * Query_limit
+ *
+ */
+#ifdef QUERY_LIMIT
+static bool
+parse_query_limit(const char *value)
+{
+  int32 limit;
+
+  if (value == NULL) {
+    reset_query_limit();
+    return(TRUE);
+  }
+  limit = pg_atoi(value, sizeof(int32), '\0');
+  if (limit <= -1) {
+    elog(ERROR, "Bad value for # of query limit (%s)", value);
+  }
+  ExecutorLimit(limit);
+  return(TRUE);
+}
+
+static bool
+show_query_limit(void)
+{
+  int limit;
+
+  limit = ExecutorGetLimit();
+  if (limit == ALL_TUPLES) {
+    elog(NOTICE, "No query limit is set");
+  } else {
+    elog(NOTICE, "query limit is %d",limit);
+  }
+  return(TRUE);
+}
+
+static bool
+reset_query_limit(void)
+{
+  ExecutorLimit(ALL_TUPLES);
+  return(TRUE);
+}
+#endif
+
 /*-----------------------------------------------------------------------*/
+
 struct VariableParsers
 {
 	const char *name;
@@ -584,6 +668,11 @@ struct VariableParsers
 	{
 		"ksqo", parse_ksqo, show_ksqo, reset_ksqo
 	},
+#ifdef QUERY_LIMIT
+	{
+		"query_limit", parse_query_limit, show_query_limit, reset_query_limit
+	},
+#endif
 	{
 		NULL, NULL, NULL, NULL
 	}

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.57 1998/10/01 02:03:58 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.58 1998/10/14 05:10:00 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -83,14 +83,18 @@ static int	queryLimit = ALL_TUPLES;
 #undef ALL_TUPLES
 #define ALL_TUPLES queryLimit
 
-int			ExecutorLimit(int limit);
-
 int
 ExecutorLimit(int limit)
 {
 	return queryLimit = limit;
 }
 
+int
+ExecutorGetLimit()
+{
+	return queryLimit;
+}
+
 #endif
 
 /* ----------------------------------------------------------------

src/bin/psql/psqlHelp.h

@@ -5,7 +5,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: psqlHelp.h,v 1.53 1998/10/08 01:10:28 tgl Exp $
+ * $Id: psqlHelp.h,v 1.54 1998/10/14 05:10:02 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -296,10 +296,10 @@ static struct _helpStruct QL_HELP[] = {
 		"set run-time environment back to default",
 #ifdef MULTIBYTE
 	"\
-\tRESET DateStyle|GEQO|R_PLANS|CLIENT_ENCODING"},
+\tRESET DateStyle|GEQO|R_PLANS|QUERY_LIMIT|CLIENT_ENCODING"},
 #else
 	"\
-\tRESET DateStyle|GEQO|R_PLANS"},
+\tRESET DateStyle|GEQO|R_PLANS|QUERY_LIMIT"},
 #endif
 	{"revoke",
 		"revoke access control from a user or group",
@@ -329,21 +329,23 @@ static struct _helpStruct QL_HELP[] = {
 \tSET DateStyle TO 'ISO'|'SQL'|'Postgres'|'European'|'US'|'NonEuropean'\n\
 set GEQO TO 'ON[=#]'|'OFF'\n\
 set R_PLANS TO 'ON'|'OFF'\n\
+set QUERY_LIMIT TO #\n\
 set CLIENT_ENCODING TO 'EUC_JP'|'SJIS'|'EUC_CN'|'EUC_KR'|'EUC_TW'|'MULE_INTERNAL'|'LATIN1'|'LATIN2'|'LATIN3'|'LATIN4'|'LATIN5'"},
 #else
 	"\
 \tSET DateStyle TO 'ISO'|'SQL'|'Postgres'|'European'|'US'|'NonEuropean'\n\
 set GEQO TO 'ON[=#]'|'OFF'\n\
-set R_PLANS TO 'ON'| 'OFF'"},
+set R_PLANS TO 'ON'| 'OFF'\n\
+set QUERY_LIMIT TO #"},
 #endif
 	{"show",
 		"show current run-time environment",
 #ifdef MULTIBYTE
 	"\
-\tSHOW DateStyle|GEQO|R_PLANS|CLIENT_ENCODING"},
+\tSHOW DateStyle|GEQO|R_PLANS|QUERY_LIMIT|CLIENT_ENCODING"},
 #else
 	"\
-\tSHOW DateStyle|GEQO|R_PLANS"},
+\tSHOW DateStyle|GEQO|R_PLANS|QUERY_LIMIT"},
 #endif
 	{"unlisten",
 		"stop listening for notification on a condition name",

src/include/executor/executor.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: executor.h,v 1.26 1998/10/08 18:30:29 momjian Exp $
+ * $Id: executor.h,v 1.27 1998/10/14 05:10:05 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -86,6 +86,10 @@ extern TupleDesc ExecutorStart(QueryDesc *queryDesc, EState *estate);
 extern TupleTableSlot *ExecutorRun(QueryDesc *queryDesc, EState *estate, int feature, int count);
 extern void ExecutorEnd(QueryDesc *queryDesc, EState *estate);
 extern HeapTuple ExecConstraints(char *caller, Relation rel, HeapTuple tuple);
+#ifdef QUERY_LIMIT
+extern int ExecutorLimit(int limit);
+extern int ExecutorGetLimit(void);
+#endif
 
 /*
  * prototypes from functions in execProcnode.c

src/man/set.l

@@ -1,6 +1,6 @@
 .\" This is -*-nroff-*-
 .\" XXX standard disclaimer belongs here....
-.\" $Header: /cvsroot/pgsql/src/man/Attic/set.l,v 1.10 1998/10/14 02:36:44 momjian Exp $
+.\" $Header: /cvsroot/pgsql/src/man/Attic/set.l,v 1.11 1998/10/14 05:10:12 momjian Exp $
 .TH SET SQL 05/14/97 PostgreSQL PostgreSQL
 .SH NAME
 set - set run-time parameters for session
@@ -76,6 +76,12 @@ by default. It's not used by GEQO anyway.
 	off	- do not use right-hand plan evaluation
 .fi
 
+.PP
+.IR QUERY_LIMIT
+restricts the number of rows returned by a query.
+The default is unlimited.
+
+
 .SH EXAMPLES
 .nf
 --