innodb change buffer记录格式

/** Structure for an SQL data tuple of fields (logical record) */struct dtuple_t {ulintinfo_bits;/*!< info bits of an index record:the default is 0; this field is usedif an index record is built froma data tuple */ulintn_fields;/*!< number of fields in dtuple */ulintn_fields_cmp;/*!< number of fields which shouldbe used in comparison servicesof rem0cmp.*; the index searchis performed by comparing only thesefields, others are ignored; thedefault value in dtuple creation isthe same value as n_fields */dfield_t*fields;/*!< fields */UT_LIST_NODE_T(dtuple_t) tuple_list;/*!< data tuples can be linked into alist using this field */};struct dfield_t{void*data;/*!< pointer to data */unsignedext:1;/*!< TRUE=externally stored, FALSE=local */unsignedlen:32;/*!< data length; UNIV_SQL_NULL if SQL null */dtype_ttype;/*!< type of data */};

ibuf_entry_build构建ibuf的逻辑记录