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Improve parsetree representation of special functions such as CURRENT_DATE.

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We implement a dozen or so parameterless functions that the SQL standard
defines special syntax for.  Up to now, that was done by converting them
into more or less ad-hoc constructs such as "'now'::text::date".  That's
messy for multiple reasons: it exposes what should be implementation
details to users, and performance is worse than it needs to be in several
cases.  To improve matters, invent a new expression node type
SQLValueFunction that can represent any of these parameterless functions.

Bump catversion because this changes stored parsetrees for rules.

Discussion: <30058.1463091294@sss.pgh.pa.us>
This commit is contained in:
Tom Lane
2016-08-16 20:33:01 -04:00
parent 4bc4cfe3bd
commit 0bb51aa967
24 changed files with 626 additions and 168 deletions
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124
src/backend/parser/gram.y
View File

@@ -165,6 +165,8 @@ static Node *makeAndExpr(Node *lexpr, Node *rexpr, int location);
static Node *makeOrExpr(Node *lexpr, Node *rexpr, int location);
static Node *makeNotExpr(Node *expr, int location);
static Node *makeAArrayExpr(List *elements, int location);
static Node *makeSQLValueFunction(SQLValueFunctionOp op, int32 typmod,
int location);
static Node *makeXmlExpr(XmlExprOp op, char *name, List *named_args,
List *args, int location);
static List *mergeTableFuncParameters(List *func_args, List *columns);
@@ -12330,143 +12332,63 @@ func_expr_common_subexpr:
}
| CURRENT_DATE
{
/*
* Translate as "'now'::text::date".
*
* We cannot use "'now'::date" because coerce_type() will
* immediately reduce that to a constant representing
* today's date. We need to delay the conversion until
* runtime, else the wrong things will happen when
* CURRENT_DATE is used in a column default value or rule.
*
* This could be simplified if we had a way to generate
* an expression tree representing runtime application
* of type-input conversion functions. (As of PG 7.3
* that is actually possible, but not clear that we want
* to rely on it.)
*
* The token location is attached to the run-time
* typecast, not to the Const, for the convenience of
* pg_stat_statements (which doesn't want these constructs
* to appear to be replaceable constants).
*/
Node *n;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
$$ = makeTypeCast(n, SystemTypeName("date"), @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_DATE, -1, @1);
}
| CURRENT_TIME
{
/*
* Translate as "'now'::text::timetz".
* See comments for CURRENT_DATE.
*/
Node *n;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
$$ = makeTypeCast(n, SystemTypeName("timetz"), @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_TIME, -1, @1);
}
| CURRENT_TIME '(' Iconst ')'
{
/*
* Translate as "'now'::text::timetz(n)".
* See comments for CURRENT_DATE.
*/
Node *n;
TypeName *d;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
d = SystemTypeName("timetz");
d->typmods = list_make1(makeIntConst($3, @3));
$$ = makeTypeCast(n, d, @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_TIME_N, $3, @1);
}
| CURRENT_TIMESTAMP
{
/*
* Translate as "now()", since we have a function that
* does exactly what is needed.
*/
$$ = (Node *) makeFuncCall(SystemFuncName("now"), NIL, @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_TIMESTAMP, -1, @1);
}
| CURRENT_TIMESTAMP '(' Iconst ')'
{
/*
* Translate as "'now'::text::timestamptz(n)".
* See comments for CURRENT_DATE.
*/
Node *n;
TypeName *d;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
d = SystemTypeName("timestamptz");
d->typmods = list_make1(makeIntConst($3, @3));
$$ = makeTypeCast(n, d, @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_TIMESTAMP_N, $3, @1);
}
| LOCALTIME
{
/*
* Translate as "'now'::text::time".
* See comments for CURRENT_DATE.
*/
Node *n;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
$$ = makeTypeCast((Node *)n, SystemTypeName("time"), @1);
$$ = makeSQLValueFunction(SVFOP_LOCALTIME, -1, @1);
}
| LOCALTIME '(' Iconst ')'
{
/*
* Translate as "'now'::text::time(n)".
* See comments for CURRENT_DATE.
*/
Node *n;
TypeName *d;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
d = SystemTypeName("time");
d->typmods = list_make1(makeIntConst($3, @3));
$$ = makeTypeCast((Node *)n, d, @1);
$$ = makeSQLValueFunction(SVFOP_LOCALTIME_N, $3, @1);
}
| LOCALTIMESTAMP
{
/*
* Translate as "'now'::text::timestamp".
* See comments for CURRENT_DATE.
*/
Node *n;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
$$ = makeTypeCast(n, SystemTypeName("timestamp"), @1);
$$ = makeSQLValueFunction(SVFOP_LOCALTIMESTAMP, -1, @1);
}
| LOCALTIMESTAMP '(' Iconst ')'
{
/*
* Translate as "'now'::text::timestamp(n)".
* See comments for CURRENT_DATE.
*/
Node *n;
TypeName *d;
n = makeStringConstCast("now", -1, SystemTypeName("text"));
d = SystemTypeName("timestamp");
d->typmods = list_make1(makeIntConst($3, @3));
$$ = makeTypeCast(n, d, @1);
$$ = makeSQLValueFunction(SVFOP_LOCALTIMESTAMP_N, $3, @1);
}
| CURRENT_ROLE
{
$$ = (Node *) makeFuncCall(SystemFuncName("current_user"), NIL, @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_ROLE, -1, @1);
}
| CURRENT_USER
{
$$ = (Node *) makeFuncCall(SystemFuncName("current_user"), NIL, @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_USER, -1, @1);
}
| SESSION_USER
{
$$ = (Node *) makeFuncCall(SystemFuncName("session_user"), NIL, @1);
$$ = makeSQLValueFunction(SVFOP_SESSION_USER, -1, @1);
}
| USER
{
$$ = (Node *) makeFuncCall(SystemFuncName("current_user"), NIL, @1);
$$ = makeSQLValueFunction(SVFOP_USER, -1, @1);
}
| CURRENT_CATALOG
{
$$ = (Node *) makeFuncCall(SystemFuncName("current_database"), NIL, @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_CATALOG, -1, @1);
}
| CURRENT_SCHEMA
{
$$ = (Node *) makeFuncCall(SystemFuncName("current_schema"), NIL, @1);
$$ = makeSQLValueFunction(SVFOP_CURRENT_SCHEMA, -1, @1);
}
| CAST '(' a_expr AS Typename ')'
{ $$ = makeTypeCast($3, $5, @1); }
@@ -14710,6 +14632,18 @@ makeAArrayExpr(List *elements, int location)
return (Node *) n;
}
static Node *
makeSQLValueFunction(SQLValueFunctionOp op, int32 typmod, int location)
{
SQLValueFunction *svf = makeNode(SQLValueFunction);
svf->op = op;
/* svf->type will be filled during parse analysis */
svf->typmod = typmod;
svf->location = location;
return (Node *) svf;
}
static Node *
makeXmlExpr(XmlExprOp op, char *name, List *named_args, List *args,
int location)

62
src/backend/parser/parse_expr.c
View File

@@ -34,7 +34,9 @@
#include "parser/parse_type.h"
#include "parser/parse_agg.h"
#include "utils/builtins.h"
#include "utils/date.h"
#include "utils/lsyscache.h"
#include "utils/timestamp.h"
#include "utils/xml.h"
@@ -107,6 +109,8 @@ static Node *transformArrayExpr(ParseState *pstate, A_ArrayExpr *a,
static Node *transformRowExpr(ParseState *pstate, RowExpr *r);
static Node *transformCoalesceExpr(ParseState *pstate, CoalesceExpr *c);
static Node *transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m);
static Node *transformSQLValueFunction(ParseState *pstate,
SQLValueFunction *svf);
static Node *transformXmlExpr(ParseState *pstate, XmlExpr *x);
static Node *transformXmlSerialize(ParseState *pstate, XmlSerialize *xs);
static Node *transformBooleanTest(ParseState *pstate, BooleanTest *b);
@@ -306,6 +310,11 @@ transformExprRecurse(ParseState *pstate, Node *expr)
result = transformMinMaxExpr(pstate, (MinMaxExpr *) expr);
break;
case T_SQLValueFunction:
result = transformSQLValueFunction(pstate,
(SQLValueFunction *) expr);
break;
case T_XmlExpr:
result = transformXmlExpr(pstate, (XmlExpr *) expr);
break;
@@ -2178,6 +2187,59 @@ transformMinMaxExpr(ParseState *pstate, MinMaxExpr *m)
return (Node *) newm;
}
static Node *
transformSQLValueFunction(ParseState *pstate, SQLValueFunction *svf)
{
/*
* All we need to do is insert the correct result type and (where needed)
* validate the typmod, so we just modify the node in-place.
*/
switch (svf->op)
{
case SVFOP_CURRENT_DATE:
svf->type = DATEOID;
break;
case SVFOP_CURRENT_TIME:
svf->type = TIMETZOID;
break;
case SVFOP_CURRENT_TIME_N:
svf->type = TIMETZOID;
svf->typmod = anytime_typmod_check(true, svf->typmod);
break;
case SVFOP_CURRENT_TIMESTAMP:
svf->type = TIMESTAMPTZOID;
break;
case SVFOP_CURRENT_TIMESTAMP_N:
svf->type = TIMESTAMPTZOID;
svf->typmod = anytimestamp_typmod_check(true, svf->typmod);
break;
case SVFOP_LOCALTIME:
svf->type = TIMEOID;
break;
case SVFOP_LOCALTIME_N:
svf->type = TIMEOID;
svf->typmod = anytime_typmod_check(false, svf->typmod);
break;
case SVFOP_LOCALTIMESTAMP:
svf->type = TIMESTAMPOID;
break;
case SVFOP_LOCALTIMESTAMP_N:
svf->type = TIMESTAMPOID;
svf->typmod = anytimestamp_typmod_check(false, svf->typmod);
break;
case SVFOP_CURRENT_ROLE:
case SVFOP_CURRENT_USER:
case SVFOP_USER:
case SVFOP_SESSION_USER:
case SVFOP_CURRENT_CATALOG:
case SVFOP_CURRENT_SCHEMA:
svf->type = NAMEOID;
break;
}
return (Node *) svf;
}
static Node *
transformXmlExpr(ParseState *pstate, XmlExpr *x)
{

43
src/backend/parser/parse_target.c
View File

@@ -1761,6 +1761,49 @@ FigureColnameInternal(Node *node, char **name)
return 2;
}
break;
case T_SQLValueFunction:
/* make these act like a function or variable */
switch (((SQLValueFunction *) node)->op)
{
case SVFOP_CURRENT_DATE:
*name = "current_date";
return 2;
case SVFOP_CURRENT_TIME:
case SVFOP_CURRENT_TIME_N:
*name = "current_time";
return 2;
case SVFOP_CURRENT_TIMESTAMP:
case SVFOP_CURRENT_TIMESTAMP_N:
*name = "current_timestamp";
return 2;
case SVFOP_LOCALTIME:
case SVFOP_LOCALTIME_N:
*name = "localtime";
return 2;
case SVFOP_LOCALTIMESTAMP:
case SVFOP_LOCALTIMESTAMP_N:
*name = "localtimestamp";
return 2;
case SVFOP_CURRENT_ROLE:
*name = "current_role";
return 2;
case SVFOP_CURRENT_USER:
*name = "current_user";
return 2;
case SVFOP_USER:
*name = "user";
return 2;
case SVFOP_SESSION_USER:
*name = "session_user";
return 2;
case SVFOP_CURRENT_CATALOG:
*name = "current_catalog";
return 2;
case SVFOP_CURRENT_SCHEMA:
*name = "current_schema";
return 2;
}
break;
case T_XmlExpr:
/* make SQL/XML functions act like a regular function */
switch (((XmlExpr *) node)->op)