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, 88 insertions, 38 deletions

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index bea1cc4d67e..9a6e3dab834 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -4253,27 +4253,47 @@ inline_function(Oid funcid, Oid result_type, Oid result_collid,
 								  ALLOCSET_DEFAULT_SIZES);
 	oldcxt = MemoryContextSwitchTo(mycxt);
 
-	/* Fetch the function body */
-	tmp = SysCacheGetAttr(PROCOID,
-						  func_tuple,
-						  Anum_pg_proc_prosrc,
-						  &isNull);
-	if (isNull)
-		elog(ERROR, "null prosrc for function %u", funcid);
-	src = TextDatumGetCString(tmp);
-
 	/*
 	 * Setup error traceback support for ereport().  This is so that we can
 	 * finger the function that bad information came from.
 	 */
 	callback_arg.proname = NameStr(funcform->proname);
-	callback_arg.prosrc = src;
+	callback_arg.prosrc = NULL;
 
 	sqlerrcontext.callback = sql_inline_error_callback;
 	sqlerrcontext.arg = (void *) &callback_arg;
 	sqlerrcontext.previous = error_context_stack;
 	error_context_stack = &sqlerrcontext;
 
+	/* Fetch the function body */
+	tmp = SysCacheGetAttr(PROCOID,
+						  func_tuple,
+						  Anum_pg_proc_prosrc,
+						  &isNull);
+	if (isNull)
+	{
+		Node	   *n;
+		List	   *querytree_list;
+
+		tmp = SysCacheGetAttr(PROCOID, func_tuple, Anum_pg_proc_prosqlbody, &isNull);
+		if (isNull)
+			elog(ERROR, "null prosrc and prosqlbody for function %u", funcid);
+
+		n = stringToNode(TextDatumGetCString(tmp));
+		if (IsA(n, List))
+			querytree_list = linitial_node(List, castNode(List, n));
+		else
+			querytree_list = list_make1(n);
+		if (list_length(querytree_list) != 1)
+			goto fail;
+		querytree = linitial(querytree_list);
+	}
+	else
+	{
+	src = TextDatumGetCString(tmp);
+
+	callback_arg.prosrc = src;
+
 	/*
 	 * Set up to handle parameters while parsing the function body.  We need a
 	 * dummy FuncExpr node containing the already-simplified arguments to pass
@@ -4317,6 +4337,7 @@ inline_function(Oid funcid, Oid result_type, Oid result_collid,
 	querytree = transformTopLevelStmt(pstate, linitial(raw_parsetree_list));
 
 	free_parsestate(pstate);
+	}
 
 	/*
 	 * The single command must be a simple "SELECT expression".
@@ -4573,12 +4594,15 @@ sql_inline_error_callback(void *arg)
 	int			syntaxerrposition;
 
 	/* If it's a syntax error, convert to internal syntax error report */
-	syntaxerrposition = geterrposition();
-	if (syntaxerrposition > 0)
+	if (callback_arg->prosrc)
 	{
-		errposition(0);
-		internalerrposition(syntaxerrposition);
-		internalerrquery(callback_arg->prosrc);
+		syntaxerrposition = geterrposition();
+		if (syntaxerrposition > 0)
+		{
+			errposition(0);
+			internalerrposition(syntaxerrposition);
+			internalerrquery(callback_arg->prosrc);
+		}
 	}
 
 	errcontext("SQL function \"%s\" during inlining", callback_arg->proname);
@@ -4690,7 +4714,6 @@ inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
 	Oid			func_oid;
 	HeapTuple	func_tuple;
 	Form_pg_proc funcform;
-	char	   *src;
 	Datum		tmp;
 	bool		isNull;
 	MemoryContext oldcxt;
@@ -4799,27 +4822,53 @@ inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
 								  ALLOCSET_DEFAULT_SIZES);
 	oldcxt = MemoryContextSwitchTo(mycxt);
 
-	/* Fetch the function body */
-	tmp = SysCacheGetAttr(PROCOID,
-						  func_tuple,
-						  Anum_pg_proc_prosrc,
-						  &isNull);
-	if (isNull)
-		elog(ERROR, "null prosrc for function %u", func_oid);
-	src = TextDatumGetCString(tmp);
-
 	/*
 	 * Setup error traceback support for ereport().  This is so that we can
 	 * finger the function that bad information came from.
 	 */
 	callback_arg.proname = NameStr(funcform->proname);
-	callback_arg.prosrc = src;
+	callback_arg.prosrc = NULL;
 
 	sqlerrcontext.callback = sql_inline_error_callback;
 	sqlerrcontext.arg = (void *) &callback_arg;
 	sqlerrcontext.previous = error_context_stack;
 	error_context_stack = &sqlerrcontext;
 
+	/* Fetch the function body */
+	tmp = SysCacheGetAttr(PROCOID,
+						  func_tuple,
+						  Anum_pg_proc_prosrc,
+						  &isNull);
+	if (isNull)
+	{
+		Node	   *n;
+
+		tmp = SysCacheGetAttr(PROCOID, func_tuple, Anum_pg_proc_prosqlbody, &isNull);
+		if (isNull)
+			elog(ERROR, "null prosrc and prosqlbody for function %u", func_oid);
+
+		n = stringToNode(TextDatumGetCString(tmp));
+		if (IsA(n, List))
+			querytree_list = linitial_node(List, castNode(List, n));
+		else
+			querytree_list = list_make1(n);
+		if (list_length(querytree_list) != 1)
+			goto fail;
+		querytree = linitial(querytree_list);
+
+		querytree_list = pg_rewrite_query(querytree);
+		if (list_length(querytree_list) != 1)
+			goto fail;
+		querytree = linitial(querytree_list);
+	}
+	else
+	{
+	char	   *src;
+
+	src = TextDatumGetCString(tmp);
+
+	callback_arg.prosrc = src;
+
 	/*
 	 * Set up to handle parameters while parsing the function body.  We can
 	 * use the FuncExpr just created as the input for
@@ -4830,18 +4879,6 @@ inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
 									  fexpr->inputcollid);
 
 	/*
-	 * Also resolve the actual function result tupdesc, if composite.  If the
-	 * function is just declared to return RECORD, dig the info out of the AS
-	 * clause.
-	 */
-	functypclass = get_expr_result_type((Node *) fexpr, NULL, &rettupdesc);
-	if (functypclass == TYPEFUNC_RECORD)
-		rettupdesc = BuildDescFromLists(rtfunc->funccolnames,
-										rtfunc->funccoltypes,
-										rtfunc->funccoltypmods,
-										rtfunc->funccolcollations);
-
-	/*
 	 * Parse, analyze, and rewrite (unlike inline_function(), we can't skip
 	 * rewriting here).  We can fail as soon as we find more than one query,
 	 * though.
@@ -4857,6 +4894,19 @@ inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
 	if (list_length(querytree_list) != 1)
 		goto fail;
 	querytree = linitial(querytree_list);
+	}
+
+	/*
+	 * Also resolve the actual function result tupdesc, if composite.  If the
+	 * function is just declared to return RECORD, dig the info out of the AS
+	 * clause.
+	 */
+	functypclass = get_expr_result_type((Node *) fexpr, NULL, &rettupdesc);
+	if (functypclass == TYPEFUNC_RECORD)
+		rettupdesc = BuildDescFromLists(rtfunc->funccolnames,
+										rtfunc->funccoltypes,
+										rtfunc->funccoltypmods,
+										rtfunc->funccolcollations);
 
 	/*
 	 * The single command must be a plain SELECT.