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Change plpgsql from using textual substitution to insert variable references
into SQL expressions, to using the newly added parser callback hooks. This allows us to do the substitutions in a more semantically-aware way: a variable reference will only be recognized where it can validly go, ie, a place where a column value or parameter would be legal, instead of the former behavior that would replace any textual match including table names and column aliases (leading to syntax errors later on). A release-note-worthy fine point is that plpgsql variable names that match fully-reserved words will now need to be quoted. This commit preserves the former behavior that variable references take precedence over any possible match to a column name. The infrastructure is in place to support the reverse precedence or throwing an error on ambiguity, but those behaviors aren't accessible yet. Most of the code changes here are associated with making the namespace data structure persist so that it can be consulted at runtime, instead of throwing it away at the end of initial function parsing. The plpgsql scanner is still doing name lookups, but that behavior is now irrelevant for SQL expressions. A future commit will deal with removing unnecessary lookups.
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7 files changed

+614
-259
lines changed

7 files changed

+614
-259
lines changed

‎src/pl/plpgsql/src/gram.y‎

Lines changed: 38 additions & 82 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.130 2009/11/05 16:58:36 tgl Exp $
12+
* $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.131 2009/11/06 18:37:54 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -520,7 +520,9 @@ decl_aliasitem : any_identifier
520520

521521
plpgsql_ns_setlocal(false);
522522

523-
nsi = plpgsql_ns_lookup(name, NULL, NULL, NULL);
523+
nsi = plpgsql_ns_lookup(plpgsql_ns_top(),
524+
name, NULL, NULL,
525+
NULL);
524526
if (nsi == NULL)
525527
{
526528
plpgsql_error_lineno = plpgsql_scanner_lineno();
@@ -550,7 +552,7 @@ decl_varname : T_WORD
550552
{
551553
/*
552554
* Since the scanner is only searching the topmost
553-
* namestack entry, getting T_SCALAR etc can only
555+
* namespace level, getting T_SCALAR etc can only
554556
* happen if the name is already declared in this
555557
* block.
556558
*/
@@ -1046,12 +1048,6 @@ for_control :
10461048
(errcode(ERRCODE_SYNTAX_ERROR),
10471049
errmsg("cursor FOR loop must have only one target variable")));
10481050

1049-
/* create loop's private RECORD variable */
1050-
plpgsql_convert_ident($2.name, &varname, 1);
1051-
new->rec = plpgsql_build_record(varname,
1052-
$2.lineno,
1053-
true);
1054-
10551051
/* can't use an unbound cursor this way */
10561052
if (cursor->cursor_explicit_expr == NULL)
10571053
ereport(ERROR,
@@ -1063,6 +1059,12 @@ for_control :
10631059
K_LOOP,
10641060
"LOOP");
10651061

1062+
/* create loop's private RECORD variable */
1063+
plpgsql_convert_ident($2.name, &varname, 1);
1064+
new->rec = plpgsql_build_record(varname,
1065+
$2.lineno,
1066+
true);
1067+
10661068
$$ = (PLpgSQL_stmt *) new;
10671069
}
10681070
else
@@ -1157,9 +1159,10 @@ for_control :
11571159
else
11581160
{
11591161
/*
1160-
* No "..", so it must be a query loop. We've prefixed an
1161-
* extra SELECT to the query text, so we need to remove that
1162-
* before performing syntax checking.
1162+
* No "..", so it must be a query loop. We've
1163+
* prefixed an extra SELECT to the query text,
1164+
* so we need to remove that before performing
1165+
* syntax checking.
11631166
*/
11641167
char *tmp_query;
11651168
PLpgSQL_stmt_fors *new;
@@ -1700,7 +1703,9 @@ exception_sect :
17001703
/*
17011704
* We use a mid-rule action to add these
17021705
* special variables to the namespace before
1703-
* parsing the WHEN clauses themselves.
1706+
* parsing the WHEN clauses themselves. The
1707+
* scope of the names extends to the end of the
1708+
* current block.
17041709
*/
17051710
PLpgSQL_exception_block *new = palloc(sizeof(PLpgSQL_exception_block));
17061711
PLpgSQL_variable *var;
@@ -1937,8 +1942,6 @@ read_sql_construct(int until,
19371942
int lno;
19381943
StringInfoData ds;
19391944
int parenlevel = 0;
1940-
Bitmapset *paramnos = NULL;
1941-
char buf[32];
19421945
PLpgSQL_expr *expr;
19431946

19441947
lno = plpgsql_scanner_lineno();
@@ -1986,31 +1989,7 @@ read_sql_construct(int until,
19861989

19871990
if (plpgsql_SpaceScanned)
19881991
appendStringInfoChar(&ds, ' ');
1989-
1990-
switch (tok)
1991-
{
1992-
case T_SCALAR:
1993-
snprintf(buf, sizeof(buf), " $%d ", yylval.scalar->dno + 1);
1994-
appendStringInfoString(&ds, buf);
1995-
paramnos = bms_add_member(paramnos, yylval.scalar->dno);
1996-
break;
1997-
1998-
case T_ROW:
1999-
snprintf(buf, sizeof(buf), " $%d ", yylval.row->dno + 1);
2000-
appendStringInfoString(&ds, buf);
2001-
paramnos = bms_add_member(paramnos, yylval.row->dno);
2002-
break;
2003-
2004-
case T_RECORD:
2005-
snprintf(buf, sizeof(buf), " $%d ", yylval.rec->dno + 1);
2006-
appendStringInfoString(&ds, buf);
2007-
paramnos = bms_add_member(paramnos, yylval.rec->dno);
2008-
break;
2009-
2010-
default:
2011-
appendStringInfoString(&ds, yytext);
2012-
break;
2013-
}
1992+
appendStringInfoString(&ds, yytext);
20141993
}
20151994

20161995
if (endtoken)
@@ -2020,7 +1999,8 @@ read_sql_construct(int until,
20201999
expr->dtype = PLPGSQL_DTYPE_EXPR;
20212000
expr->query = pstrdup(ds.data);
20222001
expr->plan = NULL;
2023-
expr->paramnos = paramnos;
2002+
expr->paramnos = NULL;
2003+
expr->ns = plpgsql_ns_top();
20242004
pfree(ds.data);
20252005

20262006
if (valid_sql)
@@ -2100,8 +2080,6 @@ static PLpgSQL_stmt *
21002080
make_execsql_stmt(const char *sqlstart, int lineno)
21012081
{
21022082
StringInfoData ds;
2103-
Bitmapset *paramnos = NULL;
2104-
char buf[32];
21052083
PLpgSQL_stmt_execsql *execsql;
21062084
PLpgSQL_expr *expr;
21072085
PLpgSQL_row *row = NULL;
@@ -2147,38 +2125,15 @@ make_execsql_stmt(const char *sqlstart, int lineno)
21472125

21482126
if (plpgsql_SpaceScanned)
21492127
appendStringInfoChar(&ds, ' ');
2150-
2151-
switch (tok)
2152-
{
2153-
case T_SCALAR:
2154-
snprintf(buf, sizeof(buf), " $%d ", yylval.scalar->dno + 1);
2155-
appendStringInfoString(&ds, buf);
2156-
paramnos = bms_add_member(paramnos, yylval.scalar->dno);
2157-
break;
2158-
2159-
case T_ROW:
2160-
snprintf(buf, sizeof(buf), " $%d ", yylval.row->dno + 1);
2161-
appendStringInfoString(&ds, buf);
2162-
paramnos = bms_add_member(paramnos, yylval.row->dno);
2163-
break;
2164-
2165-
case T_RECORD:
2166-
snprintf(buf, sizeof(buf), " $%d ", yylval.rec->dno + 1);
2167-
appendStringInfoString(&ds, buf);
2168-
paramnos = bms_add_member(paramnos, yylval.rec->dno);
2169-
break;
2170-
2171-
default:
2172-
appendStringInfoString(&ds, yytext);
2173-
break;
2174-
}
2128+
appendStringInfoString(&ds, yytext);
21752129
}
21762130

21772131
expr = palloc0(sizeof(PLpgSQL_expr));
21782132
expr->dtype = PLPGSQL_DTYPE_EXPR;
21792133
expr->query = pstrdup(ds.data);
21802134
expr->plan = NULL;
2181-
expr->paramnos = paramnos;
2135+
expr->paramnos = NULL;
2136+
expr->ns = plpgsql_ns_top();
21822137
pfree(ds.data);
21832138

21842139
check_sql_expr(expr->query);
@@ -2804,7 +2759,7 @@ check_label(const char *yytxt)
28042759
char *label_name;
28052760

28062761
plpgsql_convert_ident(yytxt, &label_name, 1);
2807-
if (plpgsql_ns_lookup_label(label_name) == NULL)
2762+
if (plpgsql_ns_lookup_label(plpgsql_ns_top(), label_name) == NULL)
28082763
yyerror("label does not exist");
28092764
return label_name;
28102765
}
@@ -3005,42 +2960,43 @@ make_case(int lineno, PLpgSQL_expr *t_expr,
30052960
*/
30062961
if (t_expr)
30072962
{
3008-
ListCell *l;
2963+
char varname[32];
30092964
PLpgSQL_var *t_var;
3010-
int t_varno;
2965+
ListCell *l;
2966+
2967+
/* use a name unlikely to collide with any user names */
2968+
snprintf(varname, sizeof(varname), "__Case__Variable_%d__",
2969+
plpgsql_nDatums);
30112970

30122971
/*
30132972
* We don't yet know the result datatype of t_expr. Build the
30142973
* variable as if it were INT4; we'll fix this at runtime if needed.
30152974
*/
30162975
t_var = (PLpgSQL_var *)
3017-
plpgsql_build_variable("*case*", lineno,
2976+
plpgsql_build_variable(varname, lineno,
30182977
plpgsql_build_datatype(INT4OID, -1),
3019-
false);
3020-
t_varno = t_var->dno;
3021-
new->t_varno = t_varno;
2978+
true);
2979+
new->t_varno = t_var->dno;
30222980

30232981
foreach(l, case_when_list)
30242982
{
30252983
PLpgSQL_case_when *cwt = (PLpgSQL_case_when *) lfirst(l);
30262984
PLpgSQL_expr *expr = cwt->expr;
30272985
StringInfoData ds;
30282986

3029-
/* Must add the CASE variable as an extra param to expression */
3030-
expr->paramnos = bms_add_member(expr->paramnos, t_varno);
3031-
30322987
/* copy expression query without SELECT keyword (expr->query + 7) */
30332988
Assert(strncmp(expr->query, "SELECT ", 7) == 0);
30342989

30352990
/* And do the string hacking */
30362991
initStringInfo(&ds);
30372992

3038-
appendStringInfo(&ds, "SELECT $%d IN (%s)",
3039-
t_varno + 1,
3040-
expr->query + 7);
2993+
appendStringInfo(&ds, "SELECT \"%s\" IN (%s)",
2994+
varname, expr->query + 7);
30412995

30422996
pfree(expr->query);
30432997
expr->query = pstrdup(ds.data);
2998+
/* Adjust expr's namespace to include the case variable */
2999+
expr->ns = plpgsql_ns_top();
30443000

30453001
pfree(ds.data);
30463002
}

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