greenplumn pl_scanner 源码
greenplumn pl_scanner 代码
文件路径：/src/pl/plpgsql/src/pl_scanner.c
/*-------------------------------------------------------------------------
*
* pl_scanner.c
* lexical scanning for PL/pgSQL
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/pl/plpgsql/src/pl_scanner.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "mb/pg_wchar.h"
#include "parser/scanner.h"
#include "plpgsql.h"
#include "pl_gram.h" /* must be after parser/scanner.h */
#include "cdb/cdbvars.h"
#include "parser/parser.h"
/* Klugy flag to tell scanner how to look up identifiers */
IdentifierLookup plpgsql_IdentifierLookup = IDENTIFIER_LOOKUP_NORMAL;
/*
* A word about keywords:
*
* We keep reserved and unreserved keywords in separate headers. Be careful
* not to put the same word in both headers. Also be sure that pl_gram.y's
* unreserved_keyword production agrees with the unreserved header. The
* reserved keywords are passed to the core scanner, so they will be
* recognized before (and instead of) any variable name. Unreserved words
* are checked for separately, usually after determining that the identifier
* isn't a known variable name. If plpgsql_IdentifierLookup is DECLARE then
* no variable names will be recognized, so the unreserved words always work.
* (Note in particular that this helps us avoid reserving keywords that are
* only needed in DECLARE sections.)
*
* In certain contexts it is desirable to prefer recognizing an unreserved
* keyword over recognizing a variable name. In particular, at the start
* of a statement we should prefer unreserved keywords unless the statement
* looks like an assignment (i.e., first token is followed by ':=' or '[').
* This rule allows most statement-introducing keywords to be kept unreserved.
* (We still have to reserve initial keywords that might follow a block
* label, unfortunately, since the method used to determine if we are at
* start of statement doesn't recognize such cases. We'd also have to
* reserve any keyword that could legitimately be followed by ':=' or '['.)
* Some additional cases are handled in pl_gram.y using tok_is_keyword().
*
* We try to avoid reserving more keywords than we have to; but there's
* little point in not reserving a word if it's reserved in the core grammar.
* Currently, the following words are reserved here but not in the core:
* BEGIN BY DECLARE EXECUTE FOREACH IF LOOP STRICT WHILE
*/
/* ScanKeywordList lookup data for PL/pgSQL keywords */
#include "pl_reserved_kwlist_d.h"
#include "pl_unreserved_kwlist_d.h"
/* Token codes for PL/pgSQL keywords */
#define PG_KEYWORD(kwname, value) value,
static const uint16 ReservedPLKeywordTokens[] = {
#include "pl_reserved_kwlist.h"
};
static const uint16 UnreservedPLKeywordTokens[] = {
#include "pl_unreserved_kwlist.h"
};
#undef PG_KEYWORD
/*
* This macro must recognize all tokens that can immediately precede a
* PL/pgSQL executable statement (that is, proc_sect or proc_stmt in the
* grammar). Fortunately, there are not very many, so hard-coding in this
* fashion seems sufficient.
*/
#define AT_STMT_START(prev_token) \
((prev_token) == ';' || \
(prev_token) == K_BEGIN || \
(prev_token) == K_THEN || \
(prev_token) == K_ELSE || \
(prev_token) == K_LOOP)
/* Auxiliary data about a token (other than the token type) */
typedef struct
{
YYSTYPE lval; /* semantic information */
YYLTYPE lloc; /* offset in scanbuf */
int leng; /* length in bytes */
} TokenAuxData;
/*
* Scanner working state. At some point we might wish to fold all this
* into a YY_EXTRA struct. For the moment, there is no need for plpgsql's
* lexer to be re-entrant, and the notational burden of passing a yyscanner
* pointer around is great enough to not want to do it without need.
*/
/* The stuff the core lexer needs */
static core_yyscan_t yyscanner = NULL;
static core_yy_extra_type core_yy;
/* The original input string */
static const char *scanorig;
/* Current token's length (corresponds to plpgsql_yylval and plpgsql_yylloc) */
static int plpgsql_yyleng;
/* Current token's code (corresponds to plpgsql_yylval and plpgsql_yylloc) */
static int plpgsql_yytoken;
/* Token pushback stack */
#define MAX_PUSHBACKS 4
static int num_pushbacks;
static int pushback_token[MAX_PUSHBACKS];
static TokenAuxData pushback_auxdata[MAX_PUSHBACKS];
/* State for plpgsql_location_to_lineno() */
static const char *cur_line_start;
static const char *cur_line_end;
static int cur_line_num;
/* Internal functions */
static int internal_yylex(TokenAuxData *auxdata);
static void push_back_token(int token, TokenAuxData *auxdata);
static void location_lineno_init(void);
/*
* This is the yylex routine called from the PL/pgSQL grammar.
* It is a wrapper around the core lexer, with the ability to recognize
* PL/pgSQL variables and return them as special T_DATUM tokens. If a
* word or compound word does not match any variable name, or if matching
* is turned off by plpgsql_IdentifierLookup, it is returned as
* T_WORD or T_CWORD respectively, or as an unreserved keyword if it
* matches one of those.
*/
int
plpgsql_yylex(void)
{
int tok1;
TokenAuxData aux1;
int kwnum;
tok1 = internal_yylex(&aux1);
if (tok1 == IDENT || tok1 == PARAM)
{
int tok2;
TokenAuxData aux2;
tok2 = internal_yylex(&aux2);
if (tok2 == '.')
{
int tok3;
TokenAuxData aux3;
tok3 = internal_yylex(&aux3);
if (tok3 == IDENT)
{
int tok4;
TokenAuxData aux4;
tok4 = internal_yylex(&aux4);
if (tok4 == '.')
{
int tok5;
TokenAuxData aux5;
tok5 = internal_yylex(&aux5);
if (tok5 == IDENT)
{
if (plpgsql_parse_tripword(aux1.lval.str,
aux3.lval.str,
aux5.lval.str,
&aux1.lval.wdatum,
&aux1.lval.cword))
tok1 = T_DATUM;
else
tok1 = T_CWORD;
}
else
{
/* not A.B.C, so just process A.B */
push_back_token(tok5, &aux5);
push_back_token(tok4, &aux4);
if (plpgsql_parse_dblword(aux1.lval.str,
aux3.lval.str,
&aux1.lval.wdatum,
&aux1.lval.cword))
tok1 = T_DATUM;
else
tok1 = T_CWORD;
}
}
else
{
/* not A.B.C, so just process A.B */
push_back_token(tok4, &aux4);
if (plpgsql_parse_dblword(aux1.lval.str,
aux3.lval.str,
&aux1.lval.wdatum,
&aux1.lval.cword))
tok1 = T_DATUM;
else
tok1 = T_CWORD;
}
}
else
{
/* not A.B, so just process A */
push_back_token(tok3, &aux3);
push_back_token(tok2, &aux2);
if (plpgsql_parse_word(aux1.lval.str,
core_yy.scanbuf + aux1.lloc,
true,
&aux1.lval.wdatum,
&aux1.lval.word))
tok1 = T_DATUM;
else if (!aux1.lval.word.quoted &&
(kwnum = ScanKeywordLookup(aux1.lval.word.ident,
&UnreservedPLKeywords)) >= 0)
{
aux1.lval.keyword = GetScanKeyword(kwnum,
&UnreservedPLKeywords);
tok1 = UnreservedPLKeywordTokens[kwnum];
}
else
tok1 = T_WORD;
}
}
else
{
/* not A.B, so just process A */
push_back_token(tok2, &aux2);
/*
* See if it matches a variable name, except in the context where
* we are at start of statement and the next token isn't
* assignment or '['. In that case, it couldn't validly be a
* variable name, and skipping the lookup allows variable names to
* be used that would conflict with plpgsql or core keywords that
* introduce statements (e.g., "comment"). Without this special
* logic, every statement-introducing keyword would effectively be
* reserved in PL/pgSQL, which would be unpleasant.
*
* If it isn't a variable name, try to match against unreserved
* plpgsql keywords. If not one of those either, it's T_WORD.
*
* Note: we must call plpgsql_parse_word even if we don't want to
* do variable lookup, because it sets up aux1.lval.word for the
* non-variable cases.
*/
if (plpgsql_parse_word(aux1.lval.str,
core_yy.scanbuf + aux1.lloc,
(!AT_STMT_START(plpgsql_yytoken) ||
(tok2 == '=' || tok2 == COLON_EQUALS ||
tok2 == '[')),
&aux1.lval.wdatum,
&aux1.lval.word))
tok1 = T_DATUM;
else if (!aux1.lval.word.quoted &&
(kwnum = ScanKeywordLookup(aux1.lval.word.ident,
&UnreservedPLKeywords)) >= 0)
{
aux1.lval.keyword = GetScanKeyword(kwnum,
&UnreservedPLKeywords);
tok1 = UnreservedPLKeywordTokens[kwnum];
}
else
tok1 = T_WORD;
}
}
else
{
/*
* Not a potential plpgsql variable name, just return the data.
*
* Note that we also come through here if the grammar pushed back a
* T_DATUM, T_CWORD, T_WORD, or unreserved-keyword token returned by a
* previous lookup cycle; thus, pushbacks do not incur extra lookup
* work, since we'll never do the above code twice for the same token.
* This property also makes it safe to rely on the old value of
* plpgsql_yytoken in the is-this-start-of-statement test above.
*/
}
plpgsql_yylval = aux1.lval;
plpgsql_yylloc = aux1.lloc;
plpgsql_yyleng = aux1.leng;
plpgsql_yytoken = tok1;
return tok1;
}
/*
* Internal yylex function. This wraps the core lexer and adds one feature:
* a token pushback stack. We also make a couple of trivial single-token
* translations from what the core lexer does to what we want, in particular
* interfacing from the core_YYSTYPE to YYSTYPE union.
*/
static int
internal_yylex(TokenAuxData *auxdata)
{
int token;
const char *yytext;
if (num_pushbacks > 0)
{
num_pushbacks--;
token = pushback_token[num_pushbacks];
*auxdata = pushback_auxdata[num_pushbacks];
}
else
{
token = core_yylex(&auxdata->lval.core_yystype,
&auxdata->lloc,
yyscanner);
/* remember the length of yytext before it gets changed */
yytext = core_yy.scanbuf + auxdata->lloc;
auxdata->leng = strlen(yytext);
/* Check for << >> and #, which the core considers operators */
if (token == Op)
{
if (strcmp(auxdata->lval.str, "<<") == 0)
token = LESS_LESS;
else if (strcmp(auxdata->lval.str, ">>") == 0)
token = GREATER_GREATER;
else if (strcmp(auxdata->lval.str, "#") == 0)
token = '#';
}
/* The core returns PARAM as ival, but we treat it like IDENT */
else if (token == PARAM)
{
auxdata->lval.str = pstrdup(yytext);
}
}
return token;
}
/*
* Push back a token to be re-read by next internal_yylex() call.
*/
static void
push_back_token(int token, TokenAuxData *auxdata)
{
if (num_pushbacks >= MAX_PUSHBACKS)
elog(ERROR, "too many tokens pushed back");
pushback_token[num_pushbacks] = token;
pushback_auxdata[num_pushbacks] = *auxdata;
num_pushbacks++;
}
/*
* Push back a single token to be re-read by next plpgsql_yylex() call.
*
* NOTE: this does not cause yylval or yylloc to "back up". Also, it
* is not a good idea to push back a token code other than what you read.
*/
void
plpgsql_push_back_token(int token)
{
TokenAuxData auxdata;
auxdata.lval = plpgsql_yylval;
auxdata.lloc = plpgsql_yylloc;
auxdata.leng = plpgsql_yyleng;
push_back_token(token, &auxdata);
}
/*
* Tell whether a token is an unreserved keyword.
*
* (If it is, its lowercased form was returned as the token value, so we
* do not need to offer that data here.)
*/
bool
plpgsql_token_is_unreserved_keyword(int token)
{
int i;
for (i = 0; i < lengthof(UnreservedPLKeywordTokens); i++)
{
if (UnreservedPLKeywordTokens[i] == token)
return true;
}
return false;
}
/*
* Append the function text starting at startlocation and extending to
* (not including) endlocation onto the existing contents of "buf".
*/
void
plpgsql_append_source_text(StringInfo buf,
int startlocation, int endlocation)
{
Assert(startlocation <= endlocation);
appendBinaryStringInfo(buf, scanorig + startlocation,
endlocation - startlocation);
}
/*
* Peek one token ahead in the input stream. Only the token code is
* made available, not any of the auxiliary info such as location.
*
* NB: no variable or unreserved keyword lookup is performed here, they will
* be returned as IDENT. Reserved keywords are resolved as usual.
*/
int
plpgsql_peek(void)
{
int tok1;
TokenAuxData aux1;
tok1 = internal_yylex(&aux1);
push_back_token(tok1, &aux1);
return tok1;
}
/*
* Peek two tokens ahead in the input stream. The first token and its
* location in the query are returned in *tok1_p and *tok1_loc, second token
* and its location in *tok2_p and *tok2_loc.
*
* NB: no variable or unreserved keyword lookup is performed here, they will
* be returned as IDENT. Reserved keywords are resolved as usual.
*/
void
plpgsql_peek2(int *tok1_p, int *tok2_p, int *tok1_loc, int *tok2_loc)
{
int tok1,
tok2;
TokenAuxData aux1,
aux2;
tok1 = internal_yylex(&aux1);
tok2 = internal_yylex(&aux2);
*tok1_p = tok1;
if (tok1_loc)
*tok1_loc = aux1.lloc;
*tok2_p = tok2;
if (tok2_loc)
*tok2_loc = aux2.lloc;
push_back_token(tok2, &aux2);
push_back_token(tok1, &aux1);
}
/*
* plpgsql_scanner_errposition
* Report an error cursor position, if possible.
*
* This is expected to be used within an ereport() call. The return value
* is a dummy (always 0, in fact).
*
* Note that this can only be used for messages emitted during initial
* parsing of a plpgsql function, since it requires the scanorig string
* to still be available.
*/
void
plpgsql_scanner_errposition(int location)
{
int pos;
if (location < 0 || scanorig == NULL)
return; /* no-op if location is unknown */
/* Convert byte offset to character number */
pos = pg_mbstrlen_with_len(scanorig, location) + 1;
/* And pass it to the ereport mechanism */
(void) internalerrposition(pos);
/* Also pass the function body string */
internalerrquery(scanorig);
}
/*
* plpgsql_yyerror
* Report a lexer or grammar error.
*
* The message's cursor position refers to the current token (the one
* last returned by plpgsql_yylex()).
* This is OK for syntax error messages from the Bison parser, because Bison
* parsers report error as soon as the first unparsable token is reached.
* Beware of using yyerror for other purposes, as the cursor position might
* be misleading!
*/
void
plpgsql_yyerror(const char *message)
{
char *yytext = core_yy.scanbuf + plpgsql_yylloc;
if (*yytext == '\0')
{
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
/* translator: %s is typically the translation of "syntax error" */
errmsg("%s at end of input", _(message)),
plpgsql_scanner_errposition(plpgsql_yylloc)));
}
else
{
/*
* If we have done any lookahead then flex will have restored the
* character after the end-of-token. Zap it again so that we report
* only the single token here. This modifies scanbuf but we no longer
* care about that.
*/
yytext[plpgsql_yyleng] = '\0';
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
/* translator: first %s is typically the translation of "syntax error" */
errmsg("%s at or near \"%s\"", _(message), yytext),
plpgsql_scanner_errposition(plpgsql_yylloc)));
}
}
/*
* Given a location (a byte offset in the function source text),
* return a line number.
*
* We expect that this is typically called for a sequence of increasing
* location values, so optimize accordingly by tracking the endpoints
* of the "current" line.
*/
int
plpgsql_location_to_lineno(int location)
{
const char *loc;
if (location < 0 || scanorig == NULL)
return 0; /* garbage in, garbage out */
loc = scanorig + location;
/* be correct, but not fast, if input location goes backwards */
if (loc < cur_line_start)
location_lineno_init();
while (cur_line_end != NULL && loc > cur_line_end)
{
cur_line_start = cur_line_end + 1;
cur_line_num++;
cur_line_end = strchr(cur_line_start, '\n');
}
return cur_line_num;
}
/* initialize or reset the state for plpgsql_location_to_lineno */
static void
location_lineno_init(void)
{
cur_line_start = scanorig;
cur_line_num = 1;
cur_line_end = strchr(cur_line_start, '\n');
}
/* return the most recently computed lineno */
int
plpgsql_latest_lineno(void)
{
return cur_line_num;
}
/*
* Called before any actual parsing is done
*
* Note: the passed "str" must remain valid until plpgsql_scanner_finish().
* Although it is not fed directly to flex, we need the original string
* to cite in error messages.
*/
void
plpgsql_scanner_init(const char *str)
{
/*
* In GPDB, temporarily disable escape_string_warning, if we're in a QE
* node. When we're parsing a PL/pgSQL function, e.g. in a CREATE FUNCTION
* command, you should've gotten the same warning from the QD node already.
* We could probably disable the warning in QE nodes altogether, not just
* in PL/pgSQL, but it can be useful for catching escaping bugs, when
* internal queries are dispatched from QD to QEs.
*/
bool save_escape_string_warning = escape_string_warning;
PG_TRY();
{
if (Gp_role == GP_ROLE_EXECUTE)
escape_string_warning = false;
/* Start up the core scanner */
yyscanner = scanner_init(str, &core_yy,
&ReservedPLKeywords, ReservedPLKeywordTokens);
if (Gp_role == GP_ROLE_EXECUTE)
escape_string_warning = save_escape_string_warning;
}
PG_CATCH();
{
if (Gp_role == GP_ROLE_EXECUTE)
escape_string_warning = save_escape_string_warning;
PG_RE_THROW();
}
PG_END_TRY();
/*
* scanorig points to the original string, which unlike the scanner's
* scanbuf won't be modified on-the-fly by flex. Notice that although
* yytext points into scanbuf, we rely on being able to apply locations
* (offsets from string start) to scanorig as well.
*/
scanorig = str;
/* Other setup */
plpgsql_IdentifierLookup = IDENTIFIER_LOOKUP_NORMAL;
plpgsql_yytoken = 0;
num_pushbacks = 0;
location_lineno_init();
}
/*
* Called after parsing is done to clean up after plpgsql_scanner_init()
*/
void
plpgsql_scanner_finish(void)
{
/* release storage */
scanner_finish(yyscanner);
/* avoid leaving any dangling pointers */
yyscanner = NULL;
scanorig = NULL;
}
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