DROP objecttype IF EXISTS for the following objects:

  table view index sequence schema type domain conversion

22 files changed, 417 insertions, 62 deletions

diff --git a/doc/src/sgml/ref/drop_conversion.sgml b/doc/src/sgml/ref/drop_conversion.sgml
index 7b1503046e..2fcfa07aa1 100644
--- a/doc/src/sgml/ref/drop_conversion.sgml
+++ b/doc/src/sgml/ref/drop_conversion.sgml
@@ -17,7 +17,7 @@
 
  <refsynopsisdiv>
 <synopsis>
-DROP CONVERSION <replaceable>name</replaceable> [ CASCADE | RESTRICT ]
+DROP CONVERSION [ IF EXISTS ] <replaceable>name</replaceable> [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
   
@@ -35,6 +35,16 @@ DROP CONVERSION <replaceable>name</replaceable> [ CASCADE | RESTRICT ]
 
    <variablelist>
     <varlistentry>
+     <term><literal>IF EXISTS</literal></term>
+     <listitem>
+      <para>
+       Do not throw an error if the conversion does not exist. 
+       A notice is issued in this case.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
      <term><replaceable>name</replaceable></term>
 
      <listitem>
diff --git a/doc/src/sgml/ref/drop_domain.sgml b/doc/src/sgml/ref/drop_domain.sgml
index d6f1a64910..7120bcb3de 100644
--- a/doc/src/sgml/ref/drop_domain.sgml
+++ b/doc/src/sgml/ref/drop_domain.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP DOMAIN <replaceable class="PARAMETER">name</replaceable> [, ...]  [ CASCADE | RESTRICT ]
+DROP DOMAIN [IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...]  [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -38,6 +38,16 @@ DROP DOMAIN <replaceable class="PARAMETER">name</replaceable> [, ...]  [ CASCADE
 
   <variablelist>
    <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the domain does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
@@ -84,7 +94,9 @@ DROP DOMAIN box;
   <title>Compatibility</title>
   
   <para>
-   This command conforms to the SQL standard.
+   This command conforms to the SQL standard, except for the
+   <literal>IF EXISTS</> option, which is a <productname>PostgreSQL</> 
+   extension.
   </para>
  </refsect1>
 
diff --git a/doc/src/sgml/ref/drop_index.sgml b/doc/src/sgml/ref/drop_index.sgml
index 34f9e74c50..1dfb4be45a 100644
--- a/doc/src/sgml/ref/drop_index.sgml
+++ b/doc/src/sgml/ref/drop_index.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP INDEX <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+DROP INDEX [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -39,6 +39,16 @@ DROP INDEX <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE |
 
   <variablelist>
    <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the index does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
diff --git a/doc/src/sgml/ref/drop_schema.sgml b/doc/src/sgml/ref/drop_schema.sgml
index 1fbb45d3e8..fed1effeea 100644
--- a/doc/src/sgml/ref/drop_schema.sgml
+++ b/doc/src/sgml/ref/drop_schema.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP SCHEMA <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+DROP SCHEMA [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -43,6 +43,16 @@ DROP SCHEMA <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE
 
   <variablelist>
    <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the schema does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
@@ -92,7 +102,9 @@ DROP SCHEMA mystuff CASCADE;
   <para>
    <command>DROP SCHEMA</command> is fully conforming with the SQL
    standard, except that the standard only allows one schema to be
-   dropped per command.
+   dropped per command, and apart from the 
+   <literal>IF EXISTS</> option, which is a <productname>PostgreSQL</> 
+   extension.
   </para>
  </refsect1>
 
diff --git a/doc/src/sgml/ref/drop_sequence.sgml b/doc/src/sgml/ref/drop_sequence.sgml
index f913270c22..e90737ac9e 100644
--- a/doc/src/sgml/ref/drop_sequence.sgml
+++ b/doc/src/sgml/ref/drop_sequence.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP SEQUENCE <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+DROP SEQUENCE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -37,6 +37,16 @@ DROP SEQUENCE <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCAD
 
   <variablelist>
    <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the sequence does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
@@ -84,7 +94,9 @@ DROP SEQUENCE serial;
   <para>
    <command>DROP SEQUENCE</command> conforms to the <acronym>SQL</acronym>
    standard, except that the standard only allows one
-   sequence to be dropped per command. 
+   sequence to be dropped per command, and apart from the 
+   <literal>IF EXISTS</> option, which is a <productname>PostgreSQL</> 
+   extension. 
   </para>
  </refsect1>
 
diff --git a/doc/src/sgml/ref/drop_table.sgml b/doc/src/sgml/ref/drop_table.sgml
index 5d93a5302e..b52efe7ff3 100644
--- a/doc/src/sgml/ref/drop_table.sgml
+++ b/doc/src/sgml/ref/drop_table.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP TABLE <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+DROP TABLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
  
@@ -49,6 +49,16 @@ DROP TABLE <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE |
 
   <variablelist>
    <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the table does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
@@ -97,7 +107,9 @@ DROP TABLE films, distributors;
 
   <para>
    This command conforms to the SQL standard, except that the standard only
-   allows one table to be dropped per command. 
+   allows one table to be dropped per command, and apart from the 
+   <literal>IF EXISTS</> option, which is a <productname>PostgreSQL</> 
+   extension.
   </para>
  </refsect1>
 
diff --git a/doc/src/sgml/ref/drop_type.sgml b/doc/src/sgml/ref/drop_type.sgml
index 669a38a594..808c25d7de 100644
--- a/doc/src/sgml/ref/drop_type.sgml
+++ b/doc/src/sgml/ref/drop_type.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP TYPE <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+DROP TYPE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -38,6 +38,16 @@ DROP TYPE <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE |
 
   <variablelist>
    <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the type does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
@@ -84,7 +94,9 @@ DROP TYPE box;
 
   <para>
    This command is similar to the corresponding command in the SQL
-   standard, but note that the <command>CREATE TYPE</command> command
+   standard, aapart from the <literal>IF EXISTS</>
+   option, which is a <productname>PostgreSQL</> extension.
+   But note that the <command>CREATE TYPE</command> command
    and the data type extension mechanisms in
    <productname>PostgreSQL</productname> differ from the SQL standard.
   </para>
diff --git a/doc/src/sgml/ref/drop_view.sgml b/doc/src/sgml/ref/drop_view.sgml
index dab40539bc..8aeecd25a1 100644
--- a/doc/src/sgml/ref/drop_view.sgml
+++ b/doc/src/sgml/ref/drop_view.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP VIEW <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+DROP VIEW [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -38,6 +38,16 @@ DROP VIEW <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE |
 
   <variablelist>
    <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the view does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>
@@ -84,7 +94,9 @@ DROP VIEW kinds;
 
   <para>
    This command conforms to the SQL standard, except that the standard only
-   allows one view to be dropped per command. 
+   allows one view to be dropped per command, and apart from the 
+   <literal>IF EXISTS</> option, which is a <productname>PostgreSQL</> 
+   extension. 
   </para>
  </refsect1>
 
diff --git a/src/backend/commands/conversioncmds.c b/src/backend/commands/conversioncmds.c
index de42788a91..69307277d2 100644
--- a/src/backend/commands/conversioncmds.c
+++ b/src/backend/commands/conversioncmds.c
@@ -98,16 +98,29 @@ CreateConversionCommand(CreateConversionStmt *stmt)
  * DROP CONVERSION
  */
 void
-DropConversionCommand(List *name, DropBehavior behavior)
+DropConversionCommand(List *name, DropBehavior behavior, bool missing_ok)
 {
 	Oid			conversionOid;
 
 	conversionOid = FindConversionByName(name);
 	if (!OidIsValid(conversionOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("conversion \"%s\" does not exist",
-						NameListToString(name))));
+	{
+		if (! missing_ok)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("conversion \"%s\" does not exist",
+							NameListToString(name))));
+		}
+		else
+		{
+			ereport(NOTICE,
+					 (errmsg("conversion \"%s\" does not exist, skipping",
+							NameListToString(name))));
+		}
+
+		return;
+	}
 
 	ConversionDrop(conversionOid, behavior);
 }
diff --git a/src/backend/commands/schemacmds.c b/src/backend/commands/schemacmds.c
index 25e914e838..5c87c15a9f 100644
--- a/src/backend/commands/schemacmds.c
+++ b/src/backend/commands/schemacmds.c
@@ -147,7 +147,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt)
  *		Removes a schema.
  */
 void
-RemoveSchema(List *names, DropBehavior behavior)
+RemoveSchema(List *names, DropBehavior behavior, bool missing_ok)
 {
 	char	   *namespaceName;
 	Oid			namespaceId;
@@ -163,9 +163,22 @@ RemoveSchema(List *names, DropBehavior behavior)
 								 CStringGetDatum(namespaceName),
 								 0, 0, 0);
 	if (!OidIsValid(namespaceId))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_SCHEMA),
-				 errmsg("schema \"%s\" does not exist", namespaceName)));
+	{
+		if (!missing_ok)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_SCHEMA),
+					 errmsg("schema \"%s\" does not exist", namespaceName)));
+		}
+		else
+		{
+			ereport(NOTICE,
+					 (errmsg("schema \"%s\" does not exist, skipping", 
+							namespaceName)));
+		}
+
+		return;
+	}
 
 	/* Permission check */
 	if (!pg_namespace_ownercheck(namespaceId, GetUserId()))
diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index dc43babaad..90b22bf4a4 100644
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -398,7 +398,7 @@ DefineType(List *names, List *parameters)
  *		Removes a datatype.
  */
 void
-RemoveType(List *names, DropBehavior behavior)
+RemoveType(List *names, DropBehavior behavior, bool missing_ok)
 {
 	TypeName   *typename;
 	Oid			typeoid;
@@ -414,10 +414,23 @@ RemoveType(List *names, DropBehavior behavior)
 	/* Use LookupTypeName here so that shell types can be removed. */
 	typeoid = LookupTypeName(typename);
 	if (!OidIsValid(typeoid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("type \"%s\" does not exist",
-						TypeNameToString(typename))));
+	{
+		if (!missing_ok)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("type \"%s\" does not exist",
+							TypeNameToString(typename))));
+		}
+		else
+		{
+			ereport(NOTICE,
+					 (errmsg("type \"%s\" does not exist, skipping",
+							TypeNameToString(typename))));
+		}
+
+		return;
+	}
 
 	tup = SearchSysCache(TYPEOID,
 						 ObjectIdGetDatum(typeoid),
@@ -779,7 +792,7 @@ DefineDomain(CreateDomainStmt *stmt)
  * This is identical to RemoveType except we insist it be a domain.
  */
 void
-RemoveDomain(List *names, DropBehavior behavior)
+RemoveDomain(List *names, DropBehavior behavior, bool missing_ok)
 {
 	TypeName   *typename;
 	Oid			typeoid;
@@ -796,10 +809,23 @@ RemoveDomain(List *names, DropBehavior behavior)
 	/* Use LookupTypeName here so that shell types can be removed. */
 	typeoid = LookupTypeName(typename);
 	if (!OidIsValid(typeoid))
-		ereport(ERROR,
-				(errcode(ERRCODE_UNDEFINED_OBJECT),
-				 errmsg("type \"%s\" does not exist",
-						TypeNameToString(typename))));
+	{
+		if (!missing_ok)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("type \"%s\" does not exist",
+							TypeNameToString(typename))));
+		}
+		else
+		{
+			ereport(NOTICE,
+					 (errmsg("type \"%s\" does not exist, skipping",
+							TypeNameToString(typename))));
+		}
+
+		return;
+	}
 
 	tup = SearchSysCache(TYPEOID,
 						 ObjectIdGetDatum(typeoid),
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 27f2fc7765..11d3a4bfd5 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -173,7 +173,7 @@ static void doNegateFloat(Value *v);
 %type <ival>	opt_lock lock_type cast_context
 %type <boolean>	opt_force opt_or_replace
 				opt_grant_grant_option opt_grant_admin_option
-				opt_nowait
+				opt_nowait 
 
 %type <boolean>	like_including_defaults
 
@@ -362,7 +362,7 @@ static void doNegateFloat(Value *v);
 
 	HANDLER HAVING HEADER HOLD HOUR_P
 
-	ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P INCLUDING INCREMENT
+	IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P INCLUDING INCREMENT
 	INDEX INHERIT INHERITS INITIALLY INNER_P INOUT INPUT_P
 	INSENSITIVE INSERT INSTEAD INT_P INTEGER INTERSECT
 	INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -2818,20 +2818,32 @@ DropOpClassStmt:
  *
  *		QUERY:
  *
- *		DROP itemtype itemname [, itemname ...] [ RESTRICT | CASCADE ]
+ *		DROP itemtype [ IF EXISTS ] itemname [, itemname ...] 
+ *           [ RESTRICT | CASCADE ]
  *
  *****************************************************************************/
 
-DropStmt:	DROP drop_type any_name_list opt_drop_behavior
+DropStmt:	DROP drop_type IF_P EXISTS any_name_list opt_drop_behavior
 				{
 					DropStmt *n = makeNode(DropStmt);
 					n->removeType = $2;
+					n->missing_ok = TRUE;
+					n->objects = $5;
+					n->behavior = $6;
+					$$ = (Node *)n;
+				}
+			| DROP drop_type any_name_list opt_drop_behavior
+				{
+					DropStmt *n = makeNode(DropStmt);
+					n->removeType = $2;
+					n->missing_ok = FALSE;
 					n->objects = $3;
 					n->behavior = $4;
 					$$ = (Node *)n;
 				}
 		;
 
+
 drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| SEQUENCE								{ $$ = OBJECT_SEQUENCE; }
 			| VIEW									{ $$ = OBJECT_VIEW; }
@@ -8159,6 +8171,7 @@ unreserved_keyword:
 			| HEADER
 			| HOLD
 			| HOUR_P
+			| IF_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
diff --git a/src/backend/parser/keywords.c b/src/backend/parser/keywords.c
index 95274cce2e..f2a060a3c7 100644
--- a/src/backend/parser/keywords.c
+++ b/src/backend/parser/keywords.c
@@ -160,6 +160,7 @@ static const ScanKeyword ScanKeywords[] = {
 	{"header", HEADER},
 	{"hold", HOLD},
 	{"hour", HOUR_P},
+	{"if",IF_P},
 	{"ilike", ILIKE},
 	{"immediate", IMMEDIATE},
 	{"immutable", IMMUTABLE},
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 6a6bc6db95..790f3d0e67 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -67,6 +67,7 @@ struct msgstrings
 	char		kind;
 	int			nonexistent_code;
 	const char *nonexistent_msg;
+	const char *skipping_msg;
 	const char *nota_msg;
 	const char *drophint_msg;
 };
@@ -75,26 +76,31 @@ static const struct msgstrings msgstringarray[] = {
 	{RELKIND_RELATION,
 		ERRCODE_UNDEFINED_TABLE,
 		gettext_noop("table \"%s\" does not exist"),
+		gettext_noop("table \"%s\" does not exist, skipping"),
 		gettext_noop("\"%s\" is not a table"),
 	gettext_noop("Use DROP TABLE to remove a table.")},
 	{RELKIND_SEQUENCE,
 		ERRCODE_UNDEFINED_TABLE,
 		gettext_noop("sequence \"%s\" does not exist"),
+		gettext_noop("sequence \"%s\" does not exist, skipping"),
 		gettext_noop("\"%s\" is not a sequence"),
 	gettext_noop("Use DROP SEQUENCE to remove a sequence.")},
 	{RELKIND_VIEW,
 		ERRCODE_UNDEFINED_TABLE,
 		gettext_noop("view \"%s\" does not exist"),
+		gettext_noop("view \"%s\" does not exist, skipping"),
 		gettext_noop("\"%s\" is not a view"),
 	gettext_noop("Use DROP VIEW to remove a view.")},
 	{RELKIND_INDEX,
 		ERRCODE_UNDEFINED_OBJECT,
 		gettext_noop("index \"%s\" does not exist"),
+		gettext_noop("index \"%s\" does not exist, skipping"),
 		gettext_noop("\"%s\" is not an index"),
 	gettext_noop("Use DROP INDEX to remove an index.")},
 	{RELKIND_COMPOSITE_TYPE,
 		ERRCODE_UNDEFINED_OBJECT,
 		gettext_noop("type \"%s\" does not exist"),
+		gettext_noop("type \"%s\" does not exist, skipping"),
 		gettext_noop("\"%s\" is not a type"),
 	gettext_noop("Use DROP TYPE to remove a type.")},
 	{'\0', 0, NULL, NULL, NULL}
@@ -132,23 +138,40 @@ DropErrorMsgWrongType(char *relname, char wrongkind, char rightkind)
  * non-existent relation
  */
 static void
-DropErrorMsgNonExistent(RangeVar *rel, char rightkind)
+DropErrorMsgNonExistent(RangeVar *rel, char rightkind, bool missing_ok)
 {
 	const struct msgstrings *rentry;
 
 	for (rentry = msgstringarray; rentry->kind != '\0'; rentry++)
 	{
 		if (rentry->kind == rightkind)
-			ereport(ERROR,
-					(errcode(rentry->nonexistent_code),
-					 errmsg(rentry->nonexistent_msg, rel->relname)));
+		{
+			if (! missing_ok)
+			{
+				ereport(ERROR,
+						(errcode(rentry->nonexistent_code),
+						 errmsg(rentry->nonexistent_msg, rel->relname)));
+			}
+			else
+			{
+				ereport(NOTICE, (errmsg(rentry->skipping_msg, rel->relname)));
+				break;
+			}
+		}
 	}
 
-	Assert(false);				/* Should be impossible */
+	Assert(rentry->kind != '\0');	   /* Should be impossible */
 }
 
-static void
-CheckDropPermissions(RangeVar *rel, char rightkind)
+/*
+ * returns false if missing_ok is true and the object does not exist,
+ * true if object exists and permissions are OK,
+ * errors otherwise
+ *
+ */
+
+static bool
+CheckDropPermissions(RangeVar *rel, char rightkind, bool missing_ok)
 {
 	Oid			relOid;
 	HeapTuple	tuple;
@@ -156,7 +179,10 @@ CheckDropPermissions(RangeVar *rel, char rightkind)
 
 	relOid = RangeVarGetRelid(rel, true);
 	if (!OidIsValid(relOid))
-		DropErrorMsgNonExistent(rel, rightkind);
+	{
+		DropErrorMsgNonExistent(rel, rightkind, missing_ok);
+		return false;
+	}
 
 	tuple = SearchSysCache(RELOID,
 						   ObjectIdGetDatum(relOid),
@@ -183,6 +209,8 @@ CheckDropPermissions(RangeVar *rel, char rightkind)
 						rel->relname)));
 
 	ReleaseSysCache(tuple);
+
+	return true;
 }
 
 /*
@@ -528,31 +556,36 @@ ProcessUtility(Node *parsetree,
 					{
 						case OBJECT_TABLE:
 							rel = makeRangeVarFromNameList(names);
-							CheckDropPermissions(rel, RELKIND_RELATION);
-							RemoveRelation(rel, stmt->behavior);
+							if (CheckDropPermissions(rel, RELKIND_RELATION,
+													 stmt->missing_ok))
+								RemoveRelation(rel, stmt->behavior);
 							break;
 
 						case OBJECT_SEQUENCE:
 							rel = makeRangeVarFromNameList(names);
-							CheckDropPermissions(rel, RELKIND_SEQUENCE);
-							RemoveRelation(rel, stmt->behavior);
+							if (CheckDropPermissions(rel, RELKIND_SEQUENCE,
+													 stmt->missing_ok))
+								RemoveRelation(rel, stmt->behavior);
 							break;
 
 						case OBJECT_VIEW:
 							rel = makeRangeVarFromNameList(names);
-							CheckDropPermissions(rel, RELKIND_VIEW);
-							RemoveView(rel, stmt->behavior);
+							if (CheckDropPermissions(rel, RELKIND_VIEW,
+													 stmt->missing_ok))
+								RemoveView(rel, stmt->behavior);
 							break;
 
 						case OBJECT_INDEX:
 							rel = makeRangeVarFromNameList(names);
-							CheckDropPermissions(rel, RELKIND_INDEX);
-							RemoveIndex(rel, stmt->behavior);
+							if (CheckDropPermissions(rel, RELKIND_INDEX,
+													 stmt->missing_ok))
+								RemoveIndex(rel, stmt->behavior);
 							break;
 
 						case OBJECT_TYPE:
 							/* RemoveType does its own permissions checks */
-							RemoveType(names, stmt->behavior);
+							RemoveType(names, stmt->behavior, 
+									   stmt->missing_ok);
 							break;
 
 						case OBJECT_DOMAIN:
@@ -560,11 +593,13 @@ ProcessUtility(Node *parsetree,
 							/*
 							 * RemoveDomain does its own permissions checks
 							 */
-							RemoveDomain(names, stmt->behavior);
+							RemoveDomain(names, stmt->behavior, 
+										 stmt->missing_ok);
 							break;
 
 						case OBJECT_CONVERSION:
-							DropConversionCommand(names, stmt->behavior);
+							DropConversionCommand(names, stmt->behavior,
+												  stmt->missing_ok);
 							break;
 
 						case OBJECT_SCHEMA:
@@ -572,7 +607,8 @@ ProcessUtility(Node *parsetree,
 							/*
 							 * RemoveSchema does its own permissions checks
 							 */
-							RemoveSchema(names, stmt->behavior);
+							RemoveSchema(names, stmt->behavior,
+										 stmt->missing_ok);
 							break;
 
 						default:
diff --git a/src/include/commands/conversioncmds.h b/src/include/commands/conversioncmds.h
index 9ad0f839a3..be04ae2cc2 100644
--- a/src/include/commands/conversioncmds.h
+++ b/src/include/commands/conversioncmds.h
@@ -18,7 +18,8 @@
 #include "nodes/parsenodes.h"
 
 extern void CreateConversionCommand(CreateConversionStmt *parsetree);
-extern void DropConversionCommand(List *conversion_name, DropBehavior behavior);
+extern void DropConversionCommand(List *conversion_name, 
+								  DropBehavior behavior, bool missing_ok);
 extern void RenameConversion(List *name, const char *newname);
 extern void AlterConversionOwner(List *name, Oid newOwnerId);
 
diff --git a/src/include/commands/schemacmds.h b/src/include/commands/schemacmds.h
index d35193d62c..96162a72a8 100644
--- a/src/include/commands/schemacmds.h
+++ b/src/include/commands/schemacmds.h
@@ -19,7 +19,7 @@
 
 extern void CreateSchemaCommand(CreateSchemaStmt *parsetree);
 
-extern void RemoveSchema(List *names, DropBehavior behavior);
+extern void RemoveSchema(List *names, DropBehavior behavior, bool missing_ok);
 extern void RemoveSchemaById(Oid schemaOid);
 
 extern void RenameSchema(const char *oldname, const char *newname);
diff --git a/src/include/commands/typecmds.h b/src/include/commands/typecmds.h
index db3afc3269..a74b6f4c12 100644
--- a/src/include/commands/typecmds.h
+++ b/src/include/commands/typecmds.h
@@ -20,10 +20,10 @@
 #define DEFAULT_TYPDELIM		','
 
 extern void DefineType(List *names, List *parameters);
-extern void RemoveType(List *names, DropBehavior behavior);
+extern void RemoveType(List *names, DropBehavior behavior, bool missing_ok);
 extern void RemoveTypeById(Oid typeOid);
 extern void DefineDomain(CreateDomainStmt *stmt);
-extern void RemoveDomain(List *names, DropBehavior behavior);
+extern void RemoveDomain(List *names, DropBehavior behavior, bool missing_ok);
 extern Oid	DefineCompositeType(const RangeVar *typevar, List *coldeflist);
 
 extern void AlterDomainDefault(List *names, Node *defaultRaw);
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 16fa572541..ed6f282150 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1278,6 +1278,7 @@ typedef struct DropStmt
 	List	   *objects;		/* list of sublists of names (as Values) */
 	ObjectType	removeType;		/* object type */
 	DropBehavior behavior;		/* RESTRICT or CASCADE behavior */
+	bool         missing_ok;    /* skip error if object is missing? */
 } DropStmt;
 
 /* ----------------------
diff --git a/src/test/regress/expected/drop_if_exists.out b/src/test/regress/expected/drop_if_exists.out
new file mode 100644
index 0000000000..10feb3f986
--- /dev/null
+++ b/src/test/regress/expected/drop_if_exists.out
@@ -0,0 +1,67 @@
+-- 
+-- IF EXISTS tests
+-- 
+-- table (will be really dropped at the end)
+DROP TABLE test_exists;
+ERROR:  table "test_exists" does not exist
+DROP TABLE IF EXISTS test_exists;
+NOTICE:  table "test_exists" does not exist, skipping
+CREATE TABLE test_exists (a int, b text);
+-- view
+DROP VIEW test_view_exists;
+ERROR:  view "test_view_exists" does not exist
+DROP VIEW IF EXISTS test_view_exists;
+NOTICE:  view "test_view_exists" does not exist, skipping
+CREATE VIEW test_view_exists AS select * from test_exists;
+DROP VIEW IF EXISTS test_view_exists;
+DROP VIEW test_view_exists;
+ERROR:  view "test_view_exists" does not exist
+-- index
+DROP INDEX test_index_exists;
+ERROR:  index "test_index_exists" does not exist
+DROP INDEX IF EXISTS test_index_exists;
+NOTICE:  index "test_index_exists" does not exist, skipping
+CREATE INDEX test_index_exists on test_exists(a);
+DROP INDEX IF EXISTS test_index_exists;
+DROP INDEX test_index_exists;
+ERROR:  index "test_index_exists" does not exist
+-- sequence
+DROP SEQUENCE test_sequence_exists;
+ERROR:  sequence "test_sequence_exists" does not exist
+DROP SEQUENCE IF EXISTS test_sequence_exists;
+NOTICE:  sequence "test_sequence_exists" does not exist, skipping
+CREATE SEQUENCE test_sequence_exists;
+DROP SEQUENCE IF EXISTS test_sequence_exists;
+DROP SEQUENCE test_sequence_exists;
+ERROR:  sequence "test_sequence_exists" does not exist
+-- schema
+DROP SCHEMA test_schema_exists;
+ERROR:  schema "test_schema_exists" does not exist
+DROP SCHEMA IF EXISTS test_schema_exists;
+NOTICE:  schema "test_schema_exists" does not exist, skipping
+CREATE SCHEMA test_schema_exists;
+DROP SCHEMA IF EXISTS test_schema_exists;
+DROP SCHEMA test_schema_exists;
+ERROR:  schema "test_schema_exists" does not exist
+-- type
+DROP TYPE test_type_exists;
+ERROR:  type "test_type_exists" does not exist
+DROP TYPE IF EXISTS test_type_exists;
+NOTICE:  type "test_type_exists" does not exist, skipping
+CREATE type test_type_exists as (a int, b text);
+DROP TYPE IF EXISTS test_type_exists;
+DROP TYPE test_type_exists;
+ERROR:  type "test_type_exists" does not exist
+-- domain
+DROP DOMAIN test_domain_exists;
+ERROR:  type "test_domain_exists" does not exist
+DROP DOMAIN IF EXISTS test_domain_exists;
+NOTICE:  type "test_domain_exists" does not exist, skipping
+CREATE domain test_domain_exists as int not null check (value > 0);
+DROP DOMAIN IF EXISTS test_domain_exists;
+DROP DOMAIN test_domain_exists;
+ERROR:  type "test_domain_exists" does not exist
+-- drop the table
+DROP TABLE IF EXISTS test_exists;
+DROP TABLE test_exists;
+ERROR:  table "test_exists" does not exist
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 3e52f6f558..d5777794bf 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -38,7 +38,7 @@ test: copy
 # ----------
 # The third group of parallel test
 # ----------
-test: constraints triggers create_misc create_aggregate create_operator inherit vacuum
+test: constraints triggers create_misc create_aggregate create_operator inherit vacuum drop_if_exists
 
 # Depends on the above
 test: create_index create_view
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index ee90a1120f..95efa9dfe3 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -49,6 +49,7 @@ test: create_misc
 test: create_aggregate
 test: create_operator
 test: create_index
+test: drop_if_exists
 test: inherit
 test: vacuum
 test: create_view
diff --git a/src/test/regress/sql/drop_if_exists.sql b/src/test/regress/sql/drop_if_exists.sql
new file mode 100644
index 0000000000..7addedaa73
--- /dev/null
+++ b/src/test/regress/sql/drop_if_exists.sql
@@ -0,0 +1,91 @@
+-- 
+-- IF EXISTS tests
+-- 
+
+-- table (will be really dropped at the end)
+
+DROP TABLE test_exists;
+
+DROP TABLE IF EXISTS test_exists;
+
+CREATE TABLE test_exists (a int, b text);
+
+-- view
+
+DROP VIEW test_view_exists;
+
+DROP VIEW IF EXISTS test_view_exists;
+
+CREATE VIEW test_view_exists AS select * from test_exists;
+
+DROP VIEW IF EXISTS test_view_exists;
+
+DROP VIEW test_view_exists;
+
+-- index
+
+DROP INDEX test_index_exists;
+
+DROP INDEX IF EXISTS test_index_exists;
+
+CREATE INDEX test_index_exists on test_exists(a);
+
+DROP INDEX IF EXISTS test_index_exists;
+
+DROP INDEX test_index_exists;
+
+-- sequence
+
+DROP SEQUENCE test_sequence_exists;
+
+DROP SEQUENCE IF EXISTS test_sequence_exists;
+
+CREATE SEQUENCE test_sequence_exists;
+
+DROP SEQUENCE IF EXISTS test_sequence_exists;
+
+DROP SEQUENCE test_sequence_exists;
+
+-- schema
+
+DROP SCHEMA test_schema_exists;
+
+DROP SCHEMA IF EXISTS test_schema_exists;
+
+CREATE SCHEMA test_schema_exists;
+
+DROP SCHEMA IF EXISTS test_schema_exists;
+
+DROP SCHEMA test_schema_exists;
+
+-- type
+
+DROP TYPE test_type_exists;
+
+DROP TYPE IF EXISTS test_type_exists;
+
+CREATE type test_type_exists as (a int, b text);
+
+DROP TYPE IF EXISTS test_type_exists;
+
+DROP TYPE test_type_exists;
+
+-- domain
+
+DROP DOMAIN test_domain_exists;
+
+DROP DOMAIN IF EXISTS test_domain_exists;
+
+CREATE domain test_domain_exists as int not null check (value > 0);
+
+DROP DOMAIN IF EXISTS test_domain_exists;
+
+DROP DOMAIN test_domain_exists;
+
+-- drop the table
+
+
+DROP TABLE IF EXISTS test_exists;
+
+DROP TABLE test_exists;
+