diff options
Diffstat (limited to 'sql/item.h')
| -rw-r--r-- | sql/item.h | 131 |
1 files changed, 127 insertions, 4 deletions
diff --git a/sql/item.h b/sql/item.h index b7e6cc6c204..0bfb2673121 100644 --- a/sql/item.h +++ b/sql/item.h @@ -44,9 +44,10 @@ class Item_field; #define MY_COLL_ALLOW_SUPERSET_CONV 1 #define MY_COLL_ALLOW_COERCIBLE_CONV 2 -#define MY_COLL_ALLOW_CONV 3 #define MY_COLL_DISALLOW_NONE 4 -#define MY_COLL_CMP_CONV 7 + +#define MY_COLL_ALLOW_CONV (MY_COLL_ALLOW_SUPERSET_CONV | MY_COLL_ALLOW_COERCIBLE_CONV) +#define MY_COLL_CMP_CONV (MY_COLL_ALLOW_CONV | MY_COLL_DISALLOW_NONE) class DTCollation { public: @@ -91,6 +92,12 @@ public: derivation= derivation_arg; repertoire= repertoire_arg; } + void set_numeric() + { + collation= &my_charset_numeric; + derivation= DERIVATION_NUMERIC; + repertoire= MY_REPERTOIRE_NUMERIC; + } void set(CHARSET_INFO *collation_arg) { collation= collation_arg; @@ -105,6 +112,7 @@ public: { switch(derivation) { + case DERIVATION_NUMERIC: return "NUMERIC"; case DERIVATION_IGNORABLE: return "IGNORABLE"; case DERIVATION_COERCIBLE: return "COERCIBLE"; case DERIVATION_IMPLICIT: return "IMPLICIT"; @@ -690,6 +698,77 @@ public: If value is not null null_value flag will be reset to FALSE. */ virtual String *val_str(String *str)=0; + + /* + Returns string representation of this item in ASCII format. + + SYNOPSIS + val_str_ascii() + str - similar to val_str(); + + NOTE + This method is introduced for performance optimization purposes. + + 1. val_str() result of some Items in string context + depends on @@character_set_results. + @@character_set_results can be set to a "real multibyte" character + set like UCS2, UTF16, UTF32. (We'll use only UTF32 in the examples + below for convenience.) + + So the default string result of such functions + in these circumstances is real multi-byte character set, like UTF32. + + For example, all numbers in string context + return result in @@character_set_results: + + SELECT CONCAT(20010101); -> UTF32 + + We do sprintf() first (to get ASCII representation) + and then convert to UTF32; + + So these kind "data sources" can use ASCII representation + internally, but return multi-byte data only because + @@character_set_results wants so. + Therefore, conversion from ASCII to UTF32 is applied internally. + + + 2. Some other functions need in fact ASCII input. + + For example, + inet_aton(), GeometryFromText(), Convert_TZ(), GET_FORMAT(). + + Similar, fields of certain type, like DATE, TIME, + when you insert string data into them, expect in fact ASCII input. + If they get non-ASCII input, for example UTF32, they + convert input from UTF32 to ASCII, and then use ASCII + representation to do further processing. + + + 3. Now imagine we pass result of a data source of the first type + to a data destination of the second type. + + What happens: + a. data source converts data from ASCII to UTF32, because + @@character_set_results wants so and passes the result to + data destination. + b. data destination gets UTF32 string. + c. data destination converts UTF32 string to ASCII, + because it needs ASCII representation to be able to handle data + correctly. + + As a result we get two steps of unnecessary conversion: + From ASCII to UTF32, then from UTF32 to ASCII. + + A better way to handle these situations is to pass ASCII + representation directly from the source to the destination. + + This is why val_str_ascii() introduced. + + RETURN + Similar to val_str() + */ + virtual String *val_str_ascii(String *str); + /* Return decimal representation of item with fixed point. @@ -864,6 +943,16 @@ public: static CHARSET_INFO *default_charset(); virtual CHARSET_INFO *compare_collation() { return NULL; } + /* + For backward compatibility, to make numeric + data types return "binary" charset in client-side metadata. + */ + virtual CHARSET_INFO *charset_for_protocol(void) const + { + return result_type() == STRING_RESULT ? collation.collation : + &my_charset_bin; + }; + virtual bool walk(Item_processor processor, bool walk_subquery, uchar *arg) { return (this->*processor)(arg); @@ -1069,6 +1158,20 @@ public: { return Field::GEOM_GEOMETRY; }; String *check_well_formed_result(String *str, bool send_error= 0); bool eq_by_collation(Item *item, bool binary_cmp, CHARSET_INFO *cs); + uint32 max_char_length() const + { return max_length / collation.collation->mbmaxlen; } + void fix_length_and_charset(uint32 max_char_length_arg, CHARSET_INFO *cs) + { + max_length= max_char_length_arg * cs->mbmaxlen; + collation.collation= cs; + } + void fix_char_length(uint32 max_char_length_arg) + { max_length= max_char_length_arg * collation.collation->mbmaxlen; } + void fix_length_and_charset_datetime(uint32 max_char_length_arg) + { + collation.set(&my_charset_numeric, DERIVATION_NUMERIC, MY_REPERTOIRE_ASCII); + fix_char_length(max_char_length_arg); + } }; @@ -1371,12 +1474,30 @@ bool agg_item_set_converter(DTCollation &coll, const char *fname, Item **args, uint nargs, uint flags, int item_sep); bool agg_item_charsets(DTCollation &c, const char *name, Item **items, uint nitems, uint flags, int item_sep); - +inline bool +agg_item_charsets_for_string_result(DTCollation &c, const char *name, + Item **items, uint nitems, + int item_sep= 1) +{ + uint flags= MY_COLL_ALLOW_SUPERSET_CONV | + MY_COLL_ALLOW_COERCIBLE_CONV; + return agg_item_charsets(c, name, items, nitems, flags, item_sep); +} +inline bool +agg_item_charsets_for_comparison(DTCollation &c, const char *name, + Item **items, uint nitems, + int item_sep= 1) +{ + uint flags= MY_COLL_ALLOW_SUPERSET_CONV | + MY_COLL_ALLOW_COERCIBLE_CONV | + MY_COLL_DISALLOW_NONE; + return agg_item_charsets(c, name, items, nitems, flags, item_sep); +} class Item_num: public Item_basic_constant { public: - Item_num() {} /* Remove gcc warning */ + Item_num() { collation.set_numeric(); } /* Remove gcc warning */ virtual Item_num *neg()= 0; Item *safe_charset_converter(CHARSET_INFO *tocs); bool check_partition_func_processor(uchar *int_arg) { return FALSE;} @@ -1561,6 +1682,8 @@ public: DBUG_ASSERT(field_type() == MYSQL_TYPE_GEOMETRY); return field->get_geometry_type(); } + CHARSET_INFO *charset_for_protocol(void) const + { return field->charset_for_protocol(); } friend class Item_default_value; friend class Item_insert_value; friend class st_select_lex_unit; |