return NOT2_SYM;
if ((symbol->tok == OR_OR_SYM) &&
!(lip->m_thd->variables.sql_mode & MODE_PIPES_AS_CONCAT))
return OR2_SYM;
return symbol->tok;
}
return 0;
}
static SYMBOL *get_hash_symbol(const char *s,
unsigned int len,bool function)
{
register uchar *hash_map;
register const char *cur_str= s;
if (len == 0) {
DBUG_PRINT("warning", ("get_hash_symbol() received a request for a zero-length symbol, which is probably a mistake."));
return(NULL);
}
if (function){
if (len>sql_functions_max_len) return 0;
hash_map= sql_functions_map;
register uint32 cur_struct= uint4korr(hash_map+((len-1)*4));
for (;;){
register uchar first_char= (uchar)cur_struct;
if (first_char == 0)
{
register int16 ires= (int16)(cur_struct>>16);
if (ires==array_elements(symbols)) return 0;
register SYMBOL *res;
if (ires>=0)
res= symbols+ires;
else
res= sql_functions-ires-1;
register uint count= (uint) (cur_str - s);
return lex_casecmp(cur_str,res->name+count,len-count) 0 : res;
}
register uchar cur_char= (uchar)to_upper_lex[(uchar)*cur_str];
if (cur_char cur_struct>>=8; if (cur_char>(uchar)cur_struct) return 0; cur_struct>>=8; cur_struct= uint4korr(hash_map+ (((uint16)cur_struct + cur_char - first_char)*4)); cur_str++; } }else{ if (len>symbols_max_len) return 0; hash_map= symbols_map; register uint32 cur_struct= uint4korr(hash_map+((len-1)*4)); for (;;){ register uchar first_char= (uchar)cur_struct; if (first_char==0){ register int16 ires= (int16)(cur_struct>>16); if (ires==array_elements(symbols)) return 0; register SYMBOL *res= symbols+ires; register uint count= (uint) (cur_str - s); return lex_casecmp(cur_str,res->name+count,len-count)!=0 0 : res; } register uchar cur_char= (uchar)to_upper_lex[(uchar)*cur_str]; if (cur_char cur_struct>>=8; if (cur_char>(uchar)cur_struct) return 0; cur_struct>>=8; cur_struct= uint4korr(hash_map+ (((uint16)cur_struct + cur_char - first_char)*4)); cur_str++; } } } 其中的get_hash_symbol便是去系统中查找关键字，第三个参数function代表是否去查找系统函数，我们这里是系统变量，不是函数，故为FALSE。所有的关键字都挂在了hash_map上，即symbols_map上。symbols_maps又是一堆处理过的数据： static uchar symbols_map[11828]= { '<', '>', 29, 0, '!', '|', 32, 0, '<', 'X', 150, 0, 'B', 'Y', 11, 1, 'A', 'W', 147, 2, 'A', 'V', 0, 4, ... 看一下这个文件的最上面的注释吧，看看有啥有用的信息，果然被找到了： 1 2 /* Do not edit this file! This is generated by gen_lex_hash.cc that seeks for a perfect hash function */ 看到了这个注释，心中豁然开朗，原来lex_hash.h是由gen_lex_hash.cc进行生成的，大家千万不要自己进行编辑此文件啊！！ 来gen_lex_hash.cc看下吧，看到了个main函数，里面是一些生成文件的操作，在generate_find_structs函数中找到了insert_symbols， 这应该是初始化我们的symbols_map数组了吧。 void insert_symbols() { size_t i= 0; SYMBOL *cur; for (cur= symbols; i hash_lex_struct *root= get_hash_struct_by_len(&root_by_len,cur->length,&max_len); insert_into_hash(root,cur->name,0,(uint) i,0); } } 看到函数的实现是循环取数组symbols,找