Postgresql源码（96）操作符的语法解析细节

mingjie

发布于 2022-12-31 17:07:13

5510

发布于 2022-12-31 17:07:13

单字符Operators

select 1+2;
3

解析过程

steps	lex	yacc规则左值	yacc规则右值	gram.y规则代码
1	SELECT 623
2	ICONST 266
3		Iconst	ICONST	$$ = $1;
4		AexprConst	Iconst	$$ = makeIntConst($1, @1)
5		c_expr	AexprConst	$$ = $1;
6		a_expr	c_expr	$$ = $1;
7	+ 43
8	ICONST 266
9		Iconst	ICONST	$$ = $1;
10		AexprConst	Iconst	$$ = makeIntConst($1, @1)
11		c_expr	AexprConst	$$ = $1;
12		a_expr	c_expr	$$ = $1;
13	; 59
14		a_expr	a_expr ‘+’ a_expr	$$ = (Node *) makeSimpleA_Expr(AEXPR_OP, “+”, $1, $3, @2);
15		target_el	a_expr	$$ = makeNode(ResTarget); …
16		target_list	target_el	$$ = list_make1($1)

select @ -5.0;
5

解析过程

steps	lex	yacc规则左值	yacc规则右值	gram.y规则代码
1	SELECT 623
2	Op 265
3		qual_Op	Op	$$ = list_make1(makeString($1))
4	- 45
5	FCONST 260
6		AexprConst	FCONST	$$ = makeFloatConst($1, @1)
7		c_expr	AexprConst	$$ = $1
8		a_expr	c_expr	$$ = $1
9	; 59
10		a_expr	‘-’ a_expr	$$ = doNegate($2, @1);
11		a_expr	qual_Op a_expr	$$ = (Node *) makeA_Expr(AEXPR_OP, $1, NULL, $2, @1)
12		target_el	a_expr	$$ = makeNode(ResTarget)
13		target_list	target_el	$$ = list_make1($1)

token来源

token	lex规则	lex规则代码
SELECT	{identifier}←{ident_start}{ident_cont}*←[A-Za-z\200-\377_]←[A-Za-z\200-\377_0-9$]	{…return yyextra->keyword_tokens[kwnum];}
Op	{operator}←{op_chars}←[~!@#^&\|`?+-*/%<>=]	{…return Op;}
FCONST	{numeric}←`(({decinteger}.{decinteger}?)	(.{decinteger}))`←decinteger

select -(-5.0);
5

解析过程

steps	lex	yacc规则左值	yacc规则右值	gram.y规则代码
1	SELECT 623
2	- 45
3	( 40
4	- 45
5	FCONST 260
6		AexprConst	FCONST	$$ = makeFloatConst($1, @1)
7		c_expr	AexprConst	$$ = $1
8		a_expr	c_expr	$$ = $1
9	) 41
10		a_expr	‘-’ a_expr	$$ = doNegate($2, @1)
11		opt_indirection	EMPTY
12	; 59
13		c_expr	‘(’ a_expr ‘)’ opt_indirection	$$ = $2
14		a_expr	c_expr	$$ = $1
15		a_expr	‘-’ a_expr	$$ = doNegate($2, @1)
16		target_el	a_expr	$$ = makeNode(ResTarget)
17		target_list	target_el	$$ = list_make1($1)

可以不加空格

select 1<<2;
select 1<< 2;
select 1 <<2;
4

解析过程（PG16）

steps	lex	yacc规则左值	yacc规则右值	gram.y规则代码
1	SELECT 623
2	ICONST 266
3		Iconst	ICONST	$$ = $1
4		AexprConst	Iconst	$$ = makeIntConst($1, @1)
5		c_expr	AexprConst	$$ = $1
6		a_expr	c_expr	$$ = $1
7	Op 265
8	ICONST 266
9		qual_Op	Op	$$ = list_make1(makeString($1))
10		Iconst	ICONST	$$ = $1
11		AexprConst	Iconst	$$ = makeIntConst($1, @1)
12		c_expr	AexprConst	$$ = $1
13		a_expr	c_expr	$$ = $1
14	; 59
15		a_expr	a_expr qual_Op a_expr	$$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, $3, @2)
16		target_el	a_expr	$$ = makeNode(ResTarget)
17		target_list	target_el	$$ = list_make1($1)

token来源（PG16）

token	lex规则	lex规则代码
SELECT	{identifier}←{ident_start}{ident_cont}*←[A-Za-z\200-\377_]←[A-Za-z\200-\377_0-9$]	{…return yyextra->keyword_tokens[kwnum];}
Op	{operator}←{op_chars}←[~!@#^&\|`?+-*/%<>=]	{…return Op;}

空格不能少

select true and false;
f

解析过程

steps	lex	yacc规则左值	yacc规则右值	gram.y规则代码
1	SELECT 623
2	TRUE_P 679
3		AexprConst	TRUE_P	$$ = makeBoolAConst(true, @1)
4		c_expr	AexprConst	$$ = $1
5		a_expr	c_expr	$$ = $1
6	AND 289
7	FALSE_P 414
8		AexprConst	FALSE_P	$$ = makeBoolAConst(false, @1)
9		c_expr	AexprConst	$$ = $1
10		a_expr	c_expr	$$ = $1
11	; 59
12		a_expr	a_expr AND a_expr	$$ = makeAndExpr($1, $3, @2)
13		target_el	a_expr	$$ = makeNode(ResTarget)
14		target_list	target_el	$$ = list_make1($1)

token来源

token	lex规则	lex规则代码
SELECT	{identifier}←{ident_start}{ident_cont}*←[A-Za-z\200-\377_]←[A-Za-z\200-\377_0-9$]	{…return yyextra->keyword_tokens[kwnum];}
TRUE_P	{identifier}←{ident_start}{ident_cont}*←[A-Za-z\200-\377_]←[A-Za-z\200-\377_0-9$]	{…return yyextra->keyword_tokens[kwnum];}
AND	{identifier}←{ident_start}{ident_cont}*←[A-Za-z\200-\377_]←[A-Za-z\200-\377_0-9$]	{…return yyextra->keyword_tokens[kwnum];}
FALSE_P	{identifier}←{ident_start}{ident_cont}*←[A-Za-z\200-\377_]←[A-Za-z\200-\377_0-9$]	{…return yyextra->keyword_tokens[kwnum];}

解析过程

steps	lex	yacc规则左值	yacc规则右值	gram.y规则代码
1	SELECT 623
2	ICONST 266
3		Iconst	ICONST	$$ = $1
4		AexprConst	Iconst	$$ = makeIntConst($1, @1)
5		c_expr	AexprConst	$$ = $1
6		a_expr	c_expr	$$ = $1
7	GREATER_EQUALS 273
8	ICONST 266
9		Iconst	ICONST	$$ = $1
10		AexprConst	Iconst	$$ = makeIntConst($1, @1)
11		c_expr	AexprConst	$$ = $1
12		a_expr	c_expr	$$ = $1
13	; 59
14		a_expr	a_expr GREATER_EQUALS a_expr	$$ = (Node *) makeSimpleA_Expr(AEXPR_OP, “>=”, $1, $3, @2)
15		target_el	a_expr	$$ = makeNode(ResTarget)
16		target_list	target_el	$$ = list_make1($1)

token来源

token	lex规则	lex规则代码
SELECT	{identifier}←{ident_start}{ident_cont}*←[A-Za-z\200-\377_]←[A-Za-z\200-\377_0-9$]	{…return yyextra->keyword_tokens[kwnum];}
GREATER_EQUALS	{greater_equals}←greater_equals “>=”	{return GREATER_EQUALS;}