Add the ability for the core grammar to have more than one parse target.

This patch essentially allows gram.y to implement a family of related
syntax trees, rather than necessarily always parsing a list of SQL
statements.  raw_parser() gains a new argument, enum RawParseMode,
to say what to do.  As proof of concept, add a mode that just parses
a TypeName without any other decoration, and use that to greatly
simplify typeStringToTypeName().

In addition, invent a new SPI entry point SPI_prepare_extended() to
allow SPI users (particularly plpgsql) to get at this new functionality.
In hopes of making this the last variant of SPI_prepare(), set up its
additional arguments as a struct rather than direct arguments, and
promise that future additions to the struct can default to zero.
SPI_prepare_cursor() and SPI_prepare_params() can perhaps go away at
some point.

Discussion: https://postgr.es/m/4165684.1607707277@sss.pgh.pa.us

3 files changed, 32 insertions, 2 deletions

diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index 6e603d007d7..9c70603434a 100644
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -15,7 +15,7 @@
 
 #include "commands/trigger.h"
 #include "lib/ilist.h"
-#include "nodes/parsenodes.h"
+#include "parser/parser.h"
 #include "utils/portal.h"
 
 
@@ -33,6 +33,15 @@ typedef struct SPITupleTable
 	SubTransactionId subid;		/* subxact in which tuptable was created */
 } SPITupleTable;
 
+/* Optional arguments for SPI_prepare_extended */
+typedef struct SPIPrepareOptions
+{
+	ParserSetupHook parserSetup;
+	void	   *parserSetupArg;
+	RawParseMode parseMode;
+	int			cursorOptions;
+} SPIPrepareOptions;
+
 /* Plans are opaque structs for standard users of SPI */
 typedef struct _SPI_plan *SPIPlanPtr;
 
@@ -113,6 +122,8 @@ extern int	SPI_execute_with_receiver(const char *src,
 extern SPIPlanPtr SPI_prepare(const char *src, int nargs, Oid *argtypes);
 extern SPIPlanPtr SPI_prepare_cursor(const char *src, int nargs, Oid *argtypes,
 									 int cursorOptions);
+extern SPIPlanPtr SPI_prepare_extended(const char *src,
+									   const SPIPrepareOptions *options);
 extern SPIPlanPtr SPI_prepare_params(const char *src,
 									 ParserSetupHook parserSetup,
 									 void *parserSetupArg,
diff --git a/src/include/executor/spi_priv.h b/src/include/executor/spi_priv.h
index 29a77781a9d..ce0f58ce687 100644
--- a/src/include/executor/spi_priv.h
+++ b/src/include/executor/spi_priv.h
@@ -95,6 +95,7 @@ typedef struct _SPI_plan
 	bool		no_snapshots;	/* let the caller handle the snapshots */
 	List	   *plancache_list; /* one CachedPlanSource per parsetree */
 	MemoryContext plancxt;		/* Context containing _SPI_plan and data */
+	RawParseMode parse_mode;	/* raw_parser() mode */
 	int			cursor_options; /* Cursor options used for planning */
 	int			nargs;			/* number of plan arguments */
 	Oid		   *argtypes;		/* Argument types (NULL if nargs is 0) */
diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h
index 09730030444..80d90027cc4 100644
--- a/src/include/parser/parser.h
+++ b/src/include/parser/parser.h
@@ -18,6 +18,24 @@
 #include "nodes/parsenodes.h"
 
 
+/*
+ * RawParseMode determines the form of the string that raw_parser() accepts:
+ *
+ * RAW_PARSE_DEFAULT: parse a semicolon-separated list of SQL commands,
+ * and return a List of RawStmt nodes.
+ *
+ * RAW_PARSE_TYPE_NAME: parse a type name, and return a one-element List
+ * containing a TypeName node.
+ *
+ * ... more to come ...
+ */
+typedef enum
+{
+	RAW_PARSE_DEFAULT = 0,
+	RAW_PARSE_TYPE_NAME
+} RawParseMode;
+
+/* Values for the backslash_quote GUC */
 typedef enum
 {
 	BACKSLASH_QUOTE_OFF,
@@ -32,7 +50,7 @@ extern PGDLLIMPORT bool standard_conforming_strings;
 
 
 /* Primary entry point for the raw parsing functions */
-extern List *raw_parser(const char *str);
+extern List *raw_parser(const char *str, RawParseMode mode);
 
 /* Utility functions exported by gram.y (perhaps these should be elsewhere) */
 extern List *SystemFuncName(char *name);