SQL-standard function body

This adds support for writing CREATE FUNCTION and CREATE PROCEDURE
statements for language SQL with a function body that conforms to the
SQL standard and is portable to other implementations.

Instead of the PostgreSQL-specific AS $$ string literal $$ syntax,
this allows writing out the SQL statements making up the body
unquoted, either as a single statement:

    CREATE FUNCTION add(a integer, b integer) RETURNS integer
        LANGUAGE SQL
        RETURN a + b;

or as a block

    CREATE PROCEDURE insert_data(a integer, b integer)
    LANGUAGE SQL
    BEGIN ATOMIC
      INSERT INTO tbl VALUES (a);
      INSERT INTO tbl VALUES (b);
    END;

The function body is parsed at function definition time and stored as
expression nodes in a new pg_proc column prosqlbody.  So at run time,
no further parsing is required.

However, this form does not support polymorphic arguments, because
there is no more parse analysis done at call time.

Dependencies between the function and the objects it uses are fully
tracked.

A new RETURN statement is introduced.  This can only be used inside
function bodies.  Internally, it is treated much like a SELECT
statement.

psql needs some new intelligence to keep track of function body
boundaries so that it doesn't send off statements when it sees
semicolons that are inside a function body.

Tested-by: Jaime Casanova <jcasanov@systemguards.com.ec>
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/1c11f1eb-f00c-43b7-799d-2d44132c02d7@2ndquadrant.com

1 files changed, 48 insertions, 31 deletions

diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index 7bb752ace3a..642683843ed 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -26,6 +26,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_func.h"
+#include "rewrite/rewriteHandler.h"
 #include "storage/proc.h"
 #include "tcop/utility.h"
 #include "utils/builtins.h"
@@ -128,21 +129,6 @@ typedef struct
 
 typedef SQLFunctionCache *SQLFunctionCachePtr;
 
-/*
- * Data structure needed by the parser callback hooks to resolve parameter
- * references during parsing of a SQL function's body.  This is separate from
- * SQLFunctionCache since we sometimes do parsing separately from execution.
- */
-typedef struct SQLFunctionParseInfo
-{
-	char	   *fname;			/* function's name */
-	int			nargs;			/* number of input arguments */
-	Oid		   *argtypes;		/* resolved types of input arguments */
-	char	  **argnames;		/* names of input arguments; NULL if none */
-	/* Note that argnames[i] can be NULL, if some args are unnamed */
-	Oid			collation;		/* function's input collation, if known */
-}			SQLFunctionParseInfo;
-
 
 /* non-export function prototypes */
 static Node *sql_fn_param_ref(ParseState *pstate, ParamRef *pref);
@@ -607,7 +593,6 @@ init_sql_fcache(FunctionCallInfo fcinfo, Oid collation, bool lazyEvalOK)
 	HeapTuple	procedureTuple;
 	Form_pg_proc procedureStruct;
 	SQLFunctionCachePtr fcache;
-	List	   *raw_parsetree_list;
 	List	   *queryTree_list;
 	List	   *resulttlist;
 	ListCell   *lc;
@@ -682,9 +667,6 @@ init_sql_fcache(FunctionCallInfo fcinfo, Oid collation, bool lazyEvalOK)
 						  procedureTuple,
 						  Anum_pg_proc_prosrc,
 						  &isNull);
-	if (isNull)
-		elog(ERROR, "null prosrc for function %u", foid);
-	fcache->src = TextDatumGetCString(tmp);
 
 	/*
 	 * Parse and rewrite the queries in the function text.  Use sublists to
@@ -695,20 +677,55 @@ init_sql_fcache(FunctionCallInfo fcinfo, Oid collation, bool lazyEvalOK)
 	 * but we'll not worry about it until the module is rewritten to use
 	 * plancache.c.
 	 */
-	raw_parsetree_list = pg_parse_query(fcache->src);
-
 	queryTree_list = NIL;
-	foreach(lc, raw_parsetree_list)
+	if (isNull)
 	{
-		RawStmt    *parsetree = lfirst_node(RawStmt, lc);
-		List	   *queryTree_sublist;
-
-		queryTree_sublist = pg_analyze_and_rewrite_params(parsetree,
-														  fcache->src,
-														  (ParserSetupHook) sql_fn_parser_setup,
-														  fcache->pinfo,
-														  NULL);
-		queryTree_list = lappend(queryTree_list, queryTree_sublist);
+		Node	   *n;
+		List	   *stored_query_list;
+
+		tmp = SysCacheGetAttr(PROCOID,
+							  procedureTuple,
+							  Anum_pg_proc_prosqlbody,
+							  &isNull);
+		if (isNull)
+			elog(ERROR, "null prosrc and prosqlbody for function %u", foid);
+
+		n = stringToNode(TextDatumGetCString(tmp));
+		if (IsA(n, List))
+			stored_query_list = linitial_node(List, castNode(List, n));
+		else
+			stored_query_list = list_make1(n);
+
+		foreach(lc, stored_query_list)
+		{
+			Query	   *parsetree = lfirst_node(Query, lc);
+			List	   *queryTree_sublist;
+
+			AcquireRewriteLocks(parsetree, true, false);
+			queryTree_sublist = pg_rewrite_query(parsetree);
+			queryTree_list = lappend(queryTree_list, queryTree_sublist);
+		}
+	}
+	else
+	{
+		List	   *raw_parsetree_list;
+
+		fcache->src = TextDatumGetCString(tmp);
+
+		raw_parsetree_list = pg_parse_query(fcache->src);
+
+		foreach(lc, raw_parsetree_list)
+		{
+			RawStmt    *parsetree = lfirst_node(RawStmt, lc);
+			List	   *queryTree_sublist;
+
+			queryTree_sublist = pg_analyze_and_rewrite_params(parsetree,
+															  fcache->src,
+															  (ParserSetupHook) sql_fn_parser_setup,
+															  fcache->pinfo,
+															  NULL);
+			queryTree_list = lappend(queryTree_list, queryTree_sublist);
+		}
 	}
 
 	/*