Reduce usage of strlen()

Changes:
- To detect automatic strlen() I removed the methods in String that
  uses 'const char *' without a length:
  - String::append(const char*)
  - Binary_string(const char *str)
  - String(const char *str, CHARSET_INFO *cs)
  - append_for_single_quote(const char *)
  All usage of append(const char*) is changed to either use
  String::append(char), String::append(const char*, size_t length) or
  String::append(LEX_CSTRING)
- Added STRING_WITH_LEN() around constant string arguments to
  String::append()
- Added overflow argument to escape_string_for_mysql() and
  escape_quotes_for_mysql() instead of returning (size_t) -1 on overflow.
  This was needed as most usage of the above functions never tested the
  result for -1 and would have given wrong results or crashes in case
  of overflows.
- Added Item_func_or_sum::func_name_cstring(), which returns LEX_CSTRING.
  Changed all Item_func::func_name()'s to func_name_cstring()'s.
  The old Item_func_or_sum::func_name() is now an inline function that
  returns func_name_cstring().str.
- Changed Item::mode_name() and Item::func_name_ext() to return
  LEX_CSTRING.
- Changed for some functions the name argument from const char * to
  to const LEX_CSTRING &:
  - Item::Item_func_fix_attributes()
  - Item::check_type_...()
  - Type_std_attributes::agg_item_collations()
  - Type_std_attributes::agg_item_set_converter()
  - Type_std_attributes::agg_arg_charsets...()
  - Type_handler_hybrid_field_type::aggregate_for_result()
  - Type_handler_geometry::check_type_geom_or_binary()
  - Type_handler::Item_func_or_sum_illegal_param()
  - Predicant_to_list_comparator::add_value_skip_null()
  - Predicant_to_list_comparator::add_value()
  - cmp_item_row::prepare_comparators()
  - cmp_item_row::aggregate_row_elements_for_comparison()
  - Cursor_ref::print_func()
- Removes String_space() as it was only used in one cases and that
  could be simplified to not use String_space(), thanks to the fixed
  my_vsnprintf().
- Added some const LEX_CSTRING's for common strings:
  - NULL_clex_str, DATA_clex_str, INDEX_clex_str.
- Changed primary_key_name to a LEX_CSTRING
- Renamed String::set_quick() to String::set_buffer_if_not_allocated() to
  clarify what the function really does.
- Rename of protocol function:
  bool store(const char *from, CHARSET_INFO *cs) to
  bool store_string_or_null(const char *from, CHARSET_INFO *cs).
  This was done to both clarify the difference between this 'store' function
  and also to make it easier to find unoptimal usage of store() calls.
- Added Protocol::store(const LEX_CSTRING*, CHARSET_INFO*)
- Changed some 'const char*' arrays to instead be of type LEX_CSTRING.
- class Item_func_units now used LEX_CSTRING for name.

Other things:
- Fixed a bug in mysql.cc:construct_prompt() where a wrong escape character
  in the prompt would cause some part of the prompt to be duplicated.
- Fixed a lot of instances where the length of the argument to
  append is known or easily obtain but was not used.
- Removed some not needed 'virtual' definition for functions that was
  inherited from the parent. I added override to these.
- Fixed Ordered_key::print() to preallocate needed buffer. Old code could
  case memory overruns.
- Simplified some loops when adding char * to a String with delimiters.

1 files changed, 25 insertions, 18 deletions

diff --git a/sql/item_vers.h b/sql/item_vers.h
index e6cfe652029..177336775c5 100644
--- a/sql/item_vers.h
+++ b/sql/item_vers.h
@@ -46,7 +46,11 @@ public:
     max_length= 1;
     return FALSE;
   }
-  virtual const char* func_name() const { return "is_history"; }
+  virtual LEX_CSTRING func_name_cstring() const override
+  {
+    static LEX_CSTRING name= {STRING_WITH_LEN("is_history") };
+   return name;
+  }
   virtual void print(String *str, enum_query_type query_type);
   Item *get_copy(THD *thd)
   { return get_item_copy<Item_func_history>(thd, this); }
@@ -57,13 +61,11 @@ class Item_func_trt_ts: public Item_datetimefunc
   TR_table::field_id_t trt_field;
 public:
   Item_func_trt_ts(THD *thd, Item* a, TR_table::field_id_t _trt_field);
-  const char *func_name() const
+  LEX_CSTRING func_name_cstring() const override
   {
-    if (trt_field == TR_table::FLD_BEGIN_TS)
-    {
-      return "trt_begin_ts";
-    }
-    return "trt_commit_ts";
+    static LEX_CSTRING begin_name=  {STRING_WITH_LEN("trt_begin_ts") };
+    static LEX_CSTRING commit_name= {STRING_WITH_LEN("trt_commit_ts") };
+    return (trt_field == TR_table::FLD_BEGIN_TS) ? begin_name : commit_name;
   }
   bool get_date(THD *thd, MYSQL_TIME *res, date_mode_t fuzzydate);
   Item *get_copy(THD *thd)
@@ -84,20 +86,23 @@ public:
   Item_func_trt_id(THD *thd, Item* a, TR_table::field_id_t _trt_field, bool _backwards= false);
   Item_func_trt_id(THD *thd, Item* a, Item* b, TR_table::field_id_t _trt_field);
 
-  const char *func_name() const
+  LEX_CSTRING func_name_cstring() const override
   {
-    switch (trt_field)
-    {
+    static LEX_CSTRING trx_name= {STRING_WITH_LEN("trt_trx_id") };
+    static LEX_CSTRING commit_name= {STRING_WITH_LEN("trt_commit_id") };
+    static LEX_CSTRING iso_name= {STRING_WITH_LEN("trt_iso_level") };
+
+    switch (trt_field) {
     case TR_table::FLD_TRX_ID:
-      return "trt_trx_id";
+      return trx_name;
     case TR_table::FLD_COMMIT_ID:
-        return "trt_commit_id";
+      return commit_name;
     case TR_table::FLD_ISO_LEVEL:
-      return "trt_iso_level";
+      return iso_name;
     default:
       DBUG_ASSERT(0);
     }
-    return NULL;
+    return NULL_clex_str;
   }
 
   bool fix_length_and_dec()
@@ -119,9 +124,10 @@ protected:
 
 public:
   Item_func_trt_trx_sees(THD *thd, Item* a, Item* b);
-  const char *func_name() const
+  LEX_CSTRING func_name_cstring() const override
   {
-    return "trt_trx_sees";
+    static LEX_CSTRING name= {STRING_WITH_LEN("trt_trx_sees") };
+    return name;
   }
   longlong val_int();
   Item *get_copy(THD *thd)
@@ -137,9 +143,10 @@ public:
   {
     accept_eq= true;
   }
-  const char *func_name() const
+  LEX_CSTRING func_name_cstring() const override
   {
-    return "trt_trx_sees_eq";
+    static LEX_CSTRING name= {STRING_WITH_LEN("trt_trx_sees_eq") };
+    return name;
   }
 };