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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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39
src/include/nodes/primnodes.h
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@@ -1050,6 +1050,45 @@ typedef struct MinMaxExpr
int location; /* token location, or -1 if unknown */
} MinMaxExpr;
/*
* SQLValueFunction - parameterless functions with special grammar productions
*
* The SQL standard categorizes some of these as <datetime value function>
* and others as <general value specification>. We call 'em SQLValueFunctions
* for lack of a better term. We store type and typmod of the result so that
* some code doesn't need to know each function individually, and because
* we would need to store typmod anyway for some of the datetime functions.
* Note that currently, all variants return non-collating datatypes, so we do
* not need a collation field; also, all these functions are stable.
*/
typedef enum SQLValueFunctionOp
{
SVFOP_CURRENT_DATE,
SVFOP_CURRENT_TIME,
SVFOP_CURRENT_TIME_N,
SVFOP_CURRENT_TIMESTAMP,
SVFOP_CURRENT_TIMESTAMP_N,
SVFOP_LOCALTIME,
SVFOP_LOCALTIME_N,
SVFOP_LOCALTIMESTAMP,
SVFOP_LOCALTIMESTAMP_N,
SVFOP_CURRENT_ROLE,
SVFOP_CURRENT_USER,
SVFOP_USER,
SVFOP_SESSION_USER,
SVFOP_CURRENT_CATALOG,
SVFOP_CURRENT_SCHEMA
} SQLValueFunctionOp;
typedef struct SQLValueFunction
{
Expr xpr;
SQLValueFunctionOp op; /* which function this is */
Oid type; /* result type/typmod */
int32 typmod;
int location; /* token location, or -1 if unknown */
} SQLValueFunction;
/*
* XmlExpr - various SQL/XML functions requiring special grammar productions
*