training_wheels_002.patch

diff --git a/contrib/Makefile b/contrib/Makefile
index 25263c0..4bd456f 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -40,6 +40,7 @@ SUBDIRS = \
 		pgstattuple	\
 		pg_visibility	\
 		postgres_fdw	\
+		require_where	\
 		seg		\
 		spi		\
 		tablefunc	\
diff --git a/contrib/require_where/Makefile b/contrib/require_where/Makefile
new file mode 100644
index 0000000..731f9fb
--- /dev/null
+++ b/contrib/require_where/Makefile
@@ -0,0 +1,15 @@
+MODULE_big = require_where
+OBJS = require_where.o
+
+PGFILEDESC = 'require_where - require DELETE and/or UPDATE to have a WHERE clause'
+
+ifdef USE_PGXS
+	PG_CONFIG = pg_config
+	PGXS = $(shell $(PG_CONFIG) --pgxs)
+	include $(PGXS)
+else
+	subdir = contrib/require_where
+	top_builddir = ../..
+	include $(top_builddir)/src/Makefile.global
+	include $(top_builddir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/require_where/require_where.c b/contrib/require_where/require_where.c
new file mode 100644
index 0000000..3f51492
--- /dev/null
+++ b/contrib/require_where/require_where.c
@@ -0,0 +1,81 @@
+/*
+ * --------------------------------------------------------------------------
+ *
+ * require_where.c
+ *
+ * Copyright (C) 2016, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * 			contrib/require_where/require_where.c
+ *
+ * --------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "parser/analyze.h"
+
+#include "utils/elog.h"
+#include "utils/guc.h"
+
+PG_MODULE_MAGIC;
+
+void		_PG_init(void);
+
+static post_parse_analyze_hook_type original_post_parse_analyze_hook = NULL;
+static bool delete_requires_where = false;
+static bool update_requires_where = false;
+
+static void
+requires_where_check(ParseState *pstate, Query *query)
+{
+
+	if (delete_requires_where && query->commandType == CMD_DELETE)
+	{
+		Assert(query->jointree != NULL);
+		if (query->jointree->quals == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_CARDINALITY_VIOLATION),
+					 errmsg("DELETE requires a WHERE clause"),
+					 errhint("To delete all rows, use \"WHERE true\" or similar")));
+	}
+
+	if (update_requires_where && query->commandType == CMD_UPDATE)
+	{
+		Assert(query->jointree != NULL);
+		if (query->jointree->quals == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_CARDINALITY_VIOLATION),
+					 errmsg("UPDATE requires a WHERE clause"),
+					 errhint("To update all rows, use \"WHERE true\" or similar")));
+	}
+
+	if (original_post_parse_analyze_hook != NULL)
+		(*original_post_parse_analyze_hook) (pstate, query);
+}
+
+void
+_PG_init(void)
+{
+	DefineCustomBoolVariable("requires_where.delete",
+								"Require every DELETE statement to have a WHERE clause.",
+								NULL,
+								&delete_requires_where,
+								false,
+								PGC_SUSET,
+								false,
+								NULL, NULL, NULL);
+
+	DefineCustomBoolVariable("requires_where.update",
+								"Require every UPDATE statement to have a WHERE clause.",
+								NULL,
+								&update_requires_where,
+								false,
+								PGC_SUSET,
+								false,
+								NULL, NULL, NULL);
+
+	original_post_parse_analyze_hook = post_parse_analyze_hook;
+	post_parse_analyze_hook = requires_where_check;
+}
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index c8708ec..48ca717 100644
--- a/doc/src/sgml/contrib.sgml
+++ b/doc/src/sgml/contrib.sgml
@@ -135,6 +135,7 @@ CREATE EXTENSION <replaceable>module_name</> FROM unpackaged;
  &pgtrgm;
  &pgvisibility;
  &postgres-fdw;
+ &require-where;
  &seg;
  &sepgsql;
  &contrib-spi;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 4383711..737565e 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -140,6 +140,7 @@
 <!ENTITY pgtrgm          SYSTEM "pgtrgm.sgml">
 <!ENTITY pgvisibility    SYSTEM "pgvisibility.sgml">
 <!ENTITY postgres-fdw    SYSTEM "postgres-fdw.sgml">
+<!ENTITY require-where   SYSTEM "require-where.sgml">
 <!ENTITY seg             SYSTEM "seg.sgml">
 <!ENTITY contrib-spi     SYSTEM "contrib-spi.sgml">
 <!ENTITY sepgsql         SYSTEM "sepgsql.sgml">
diff --git a/doc/src/sgml/require-where.sgml b/doc/src/sgml/require-where.sgml
new file mode 100644
index 0000000..7336f58
--- /dev/null
+++ b/doc/src/sgml/require-where.sgml
@@ -0,0 +1,89 @@
+<!-- doc/src/sgml/require-where.sgml -->
+
+<sect1 id="require-where" xreflabel="require_where">
+ <title>require-where</title>
+
+ <indexterm zone="require-where">
+  <primary>require_where</primary>
+ </indexterm>
+
+ <para>
+  This module allows a superuser to require that WHERE clauses on
+  either DELETE or UPDATE not be empty using a custom GUC to control
+  each.
+ </para>
+
+ <para>
+  To use this module, you must include <literal>require_where</literal>
+  in the <xref linkend="guc-shared-preload-libraries"> parameter.
+ </para>
+
+ <para>
+  Here is an example showing how to set up a database cluster with
+  <literal>require_where</literal>.
+<screen>
+$ psql -U postgres
+# SHOW shared_preload_libraries; /* Make sure not to clobber something by accident */
+
+If you found something, 
+# ALTER SYSTEM SET shared_preload_libraries='the,stuff,you,found,require_where';
+
+Otherwise,
+# ALTER SYSTEM SET shared_preload_libraries='require_where';
+
+Then restart <productname>PostgreSQL</productname>
+</screen>
+ </para>
+
+
+ <sect2>
+  <title>GUC Parameters</title>
+
+  <variablelist>
+   <varlistentry id="guc-require-where-delete" xreflabel="require_where.delete">
+    <term>
+     <varname>require_where.delete</varname> (<type>boolean</type>)
+     <indexterm>
+      <primary><varname>require_where.delete</varname> configuration parameter</primary>
+     </indexterm>
+    </term>
+    <listitem>
+     <para>
+      This parameter defaults to <literal>false</literal>.  When set
+      to <literal>true</literal>, every <literal>DELETE</literal> requires
+      some kind of <literal>WHERE</literal> clause in order to
+      execute.  When <literal>DELETE</literal> is meant to span the
+      entire relation, one can issue a <literal>WHERE true</literal>
+      or equivalent.
+     </para>
+    </listitem>
+   </varlistentry>
+   <varlistentry id="guc-require-where-update" xreflabel="require_where.update">
+    <term>
+     <varname>require_where.update</varname> (<type>boolean</type>)
+     <indexterm>
+      <primary><varname>require_where.update</varname> configuration parameter</primary>
+     </indexterm>
+    </term>
+    <listitem>
+     <para>
+      This parameter defaults to <literal>false</literal>.  When set
+      to <literal>true</literal>, every <literal>UPDATE</literal> requires
+      some kind of <literal>WHERE</literal> clause in order to
+      execute.  When <literal>UPDATE</literal> is meant to span the
+      entire relation, one can issue a <literal>WHERE true</literal>
+      or equivalent.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+ </sect2>
+
+ <sect2>
+  <title>Authors</title>
+
+  <para>
+   David Fetter <email>david@fetter.org</email>, Oakland, California, USA
+  </para>
+ </sect2>
+</sect1>