Fix for Bug# 4200 "Parse error on LIKE ESCAPE with parameter binding"

Now ESCAPE in LIKE will accept not only string literal but constant 
delimited expression.

mysql-test/r/func_like.result

@@ -45,6 +45,12 @@ a\b
 select * from t1 where a like 'a\\%' escape '#' and a like 'a\\\\b';
 a
 a\b
+prepare stmt1 from 'select * from t1 where a like \'a\\%\' escape ?';
+set @esc='#';
+execute stmt1 using @esc;
+a
+a\b
+deallocate prepare stmt1;
 drop table t1;
 create table t1 (a datetime);
 insert into t1 values ('2004-03-11 12:00:21');

mysql-test/t/func_like.test

@@ -25,14 +25,23 @@ select * from t1 where a like "%abc\d%";
 
 drop table t1;
 
+create table t1 (a varchar(10), key(a));
+
 #
 # Bug #2231
 #
-
-create table t1 (a varchar(10), key(a));
 insert into t1 values ('a'), ('a\\b');
 select * from t1 where a like 'a\\%' escape '#';
 select * from t1 where a like 'a\\%' escape '#' and a like 'a\\\\b';
+
+#
+# Bug #4200: Prepared statement parameter as argument to ESCAPE
+#
+prepare stmt1 from 'select * from t1 where a like \'a\\%\' escape ?';
+set @esc='#';
+execute stmt1 using @esc;  
+deallocate prepare stmt1;
+
 drop table t1;
 
 #

sql/item_cmpfunc.cc

@@ -2151,9 +2151,22 @@ Item_func::optimize_type Item_func_like::select_optimize() const
 bool Item_func_like::fix_fields(THD *thd, TABLE_LIST *tlist, Item ** ref)
 {
   DBUG_ASSERT(fixed == 0);
-  if (Item_bool_func2::fix_fields(thd, tlist, ref))
+  if (Item_bool_func2::fix_fields(thd, tlist, ref) ||
+      escape_item->fix_fields(thd, tlist, &escape_item))
     return 1;
 
+  if (!escape_item->const_during_execution())
+  {
+    my_error(ER_WRONG_ARGUMENTS,MYF(0),"ESCAPE");
+    return 1;
+  }
+  
+  if (escape_item->const_item())
+  {
+    /* If we are on execution stage */
+    String *escape_str= escape_item->val_str(&tmp_value1);
+    escape= escape_str ? *(escape_str->ptr()) : '\\';
+ 
     /*
       We could also do boyer-more for non-const items, but as we would have to
       recompute the tables for each row it's not worth it.
@@ -2181,7 +2194,6 @@ bool Item_func_like::fix_fields(THD *thd, TABLE_LIST *tlist, Item ** ref)
         for (; *tmp != wild_many && *tmp != wild_one && *tmp != escape; tmp++) ;
         canDoTurboBM = (tmp == last) && !use_mb(args[0]->collation.collation);
       }
-
       if (canDoTurboBM)
       {
         pattern     = first + 1;
@@ -2196,6 +2208,7 @@ bool Item_func_like::fix_fields(THD *thd, TABLE_LIST *tlist, Item ** ref)
         DBUG_PRINT("info",("done"));
       }
     }
+  }
   return 0;
 }
 

sql/item_cmpfunc.h

@@ -841,12 +841,14 @@ class Item_func_like :public Item_bool_func2
   bool turboBM_matches(const char* text, int text_len) const;
   enum { alphabet_size = 256 };
 
+  Item *escape_item;
+
 public:
   char escape;
 
-  Item_func_like(Item *a,Item *b, char* escape_arg)
+  Item_func_like(Item *a,Item *b, Item *escape_arg)
     :Item_bool_func2(a,b), canDoTurboBM(false), pattern(0), pattern_len(0), 
-     bmGs(0), bmBc(0), escape(*escape_arg) {}
+     bmGs(0), bmBc(0), escape_item(escape_arg) {}
   longlong val_int();
   enum Functype functype() const { return LIKE_FUNC; }
   optimize_type select_optimize() const;

sql/sql_help.cc

@@ -626,7 +626,7 @@ SQL_SELECT *prepare_select_for_name(THD *thd, const char *mask, uint mlen,
 {
   Item *cond= new Item_func_like(new Item_field(pfname),
 				 new Item_string(mask,mlen,pfname->charset()),
-				 (char*) "\\");
+				 new Item_string("\\",1,&my_charset_latin1));
   if (thd->is_fatal_error)
     return 0;					// OOM
   return prepare_simple_select(thd,cond,tables,table,error);

sql/sql_yacc.yy

@@ -606,7 +606,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b,int *yystacksize);
 
 %type <simple_string>
 	remember_name remember_end opt_ident opt_db text_or_password
-	opt_escape opt_constraint constraint
+	opt_constraint constraint
 
 %type <string>
 	text_string opt_gconcat_separator
@@ -634,7 +634,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b,int *yystacksize);
 	using_list expr_or_default set_expr_or_default interval_expr
 	param_marker singlerow_subselect singlerow_subselect_init
 	exists_subselect exists_subselect_init geometry_function
-	signed_literal now_or_signed_literal
+	signed_literal now_or_signed_literal opt_escape
 
 %type <item_num>
 	NUM_literal
@@ -3570,8 +3570,12 @@ having_clause:
 	;
 
 opt_escape:
-	ESCAPE_SYM TEXT_STRING_literal	{ $$= $2.str; }
-	| /* empty */			{ $$= (char*) "\\"; };
+	ESCAPE_SYM simple_expr { $$= $2; }
+	| /* empty */
+          { 
+            $$= new Item_string("\\", 1, &my_charset_latin1);
+          }
+        ;
 
 
 /*