Added IF EXISTS to DROP PROCEDURE|FUNCTION.

Changed another unecessary use of Item_string into LEX_STRING (in sp_pcontext).


Docs/sp-implemented.txt:
  Added IF EXISTS to DROP PROCEDURE|FUNCTION
mysql-test/r/sp-error.result:
  Added IF EXISTS to DROP PROCEDURE|FUNCTION
mysql-test/t/sp-error.test:
  Added IF EXISTS to DROP PROCEDURE|FUNCTION
sql/sp_pcontext.cc:
  Changed another unecessary use of Item_string into LEX_STRING.
sql/sp_pcontext.h:
  Changed another unecessary use of Item_string into LEX_STRING.
sql/sql_parse.cc:
  Added IF EXISTS to DROP PROCEDURE|FUNCTION
sql/sql_yacc.yy:
  Added IF EXISTS to DROP PROCEDURE|FUNCTION

Docs/sp-implemented.txt

@@ -35,7 +35,7 @@ List of what's implemented:
     Is parsed, but a no-op (as there are no characteristics implemented yet).
     CASCADE/RESTRICT is not implemented (and CASCADE probably will not be).
 
-  - DROP PROCEDURE|FUNCTION name
+  - DROP PROCEDURE|FUNCTION [IF EXISTS] name
     CASCADE/RESTRICT is not implemented (and CASCADE probably will not be).
 
   - CALL name (args)

mysql-test/r/sp-error.result

@@ -25,6 +25,9 @@ drop function foo;
 FUNCTION foo does not exist
 call foo();
 PROCEDURE foo does not exist
+drop procedure if exists foo;
+Warnings:
+Warning	1256	PROCEDURE foo does not exist
 create procedure foo()
 foo: loop
 leave bar;

mysql-test/t/sp-error.test

@@ -48,6 +48,7 @@ drop procedure foo|
 drop function foo|
 --error 1256
 call foo()|
+drop procedure if exists foo|
 
 # LEAVE/ITERATE with no match
 --error 1259

sql/sp_pcontext.cc

@@ -65,13 +65,12 @@ sp_pcontext::find_pvar(LEX_STRING *name)
 
   while (i-- > 0)
   {
-    uint len= m_pvar[i].name->const_string()->length();
+    uint len= (m_pvar[i].name.length > name->length ?
+	       m_pvar[i].name.length : name->length);
 
-    if (name->length > len)
-      len= name->length;
     if (my_strncasecmp(system_charset_info,
 		       name->str,
-		       m_pvar[i].name->const_string()->ptr(),
+		       m_pvar[i].name.str,
 		       len) == 0)
     {
       return m_pvar + i;
@@ -90,8 +89,8 @@ sp_pcontext::push(LEX_STRING *name, enum enum_field_types type,
   {
     if (m_i == m_framesize)
       m_framesize += 1;
-    m_pvar[m_i].name= new Item_string(name->str, name->length,
-				      default_charset_info);
+    m_pvar[m_i].name.str= name->str;
+    m_pvar[m_i].name.length= name->length,
     m_pvar[m_i].type= type;
     m_pvar[m_i].mode= mode;
     m_pvar[m_i].offset= m_i;

sql/sp_pcontext.h

@@ -31,7 +31,7 @@ typedef enum
 
 typedef struct
 {
-  Item_string *name;
+  LEX_STRING name;
   enum enum_field_types type;
   sp_param_mode_t mode;
   uint offset;			// Offset in current frame

sql/sql_parse.cc

@@ -3101,6 +3101,15 @@ mysql_execute_command(THD *thd)
 	send_ok(thd);
 	break;
       case SP_KEY_NOT_FOUND:
+	if (lex->drop_if_exists)
+	{
+	  push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+			      ER_SP_DOES_NOT_EXIST, ER(ER_SP_DOES_NOT_EXIST),
+			      SP_COM_STRING(lex), lex->udf.name.str);
+	  res= 0;
+	  send_ok(thd);
+	  break;
+	}
 	net_printf(thd, ER_SP_DOES_NOT_EXIST, SP_COM_STRING(lex),
 		   lex->udf.name.str);
 	goto error;

sql/sql_yacc.yy

@@ -3699,17 +3699,19 @@ drop:
 	    lex->drop_if_exists=$3;
 	    lex->name=$4.str;
 	 }
-	| DROP FUNCTION_SYM IDENT_sys opt_restrict
+	| DROP FUNCTION_SYM if_exists IDENT_sys opt_restrict
 	  {
 	    LEX *lex=Lex;
 	    lex->sql_command = SQLCOM_DROP_FUNCTION;
-	    lex->udf.name= $3;
+	    lex->drop_if_exists= $3;
+	    lex->udf.name= $4;
 	  }
-	| DROP PROCEDURE ident opt_restrict
+	| DROP PROCEDURE if_exists IDENT_sys opt_restrict
 	  {
 	    LEX *lex=Lex;
 	    lex->sql_command = SQLCOM_DROP_PROCEDURE;
-	    lex->udf.name= $3;
+	    lex->drop_if_exists= $3;
+	    lex->udf.name= $4;
 	  }
 	;