Added NATIVE binding support

doc/sql.extensions/README.set_bind.md

@@ -11,15 +11,30 @@
 ### Syntax is:
 
 ```sql
-SET BIND OF type1 TO type2;
+SET BIND OF type-from TO { type-to | LEGACY };
 SET BIND OF type NATIVE;
 ```
 
 ### Description:
 
-Makes it possible to define rules of describing types of returned to the client columns in non-standard way - `type1` is replaced with `type2`, automatic data coercion takes place.
+Makes it possible to define rules of describing types of returned to the client columns in non-standard way -
+`type-from` is replaced with `type-to`, automatic data coercion takes place.
+
+Except SQL-statement there are two more ways to specify data coercion - tag `isc_dpb_bind` in DPB
+and `SetBind` parameter in firebird.conf & databases.conf. The later the rule is introduced (.conf->DPB->SQL)
+the higher priotiy it has. I.e. one can override any preconfigured settings from SQL statement.
+
+When incomplete type definition is used (i.e. `CHAR` instead `CHAR(n)`) in left part of `SET BIND` coercion
+will take place for all `CHAR` columns, not only default `CHAR(1)`.
+When incomplete type definiton is used in right side of the statement (TO part) firebird engine will define missing
+details about that type automatically based on source column.
+
+Special `TO` part format `LEGACY` is used when datatype, missing in previous FB version, should be represented in
+a way, understandable by old client software (may be with some data losses). For example, `NUMERIC(38)` in legacy
+form will be represented as `NUMERIC(18)`.
+
+Setting `NATIVE` means `type` will be used as if there were no previous rules for it.
 
-When incomplete type definition is used (i.e. `CHAR` instead `CHAR(n)`) in left part of `SET BIND` coercion will take place for all `CHAR` columns, not only default `CHAR(1)`. When incomplete type definiton is used in right side of the statement firebird engine will define missing parts automatically based on source column.
 
 ### Samples:
 

src/dsql/StmtNodes.cpp

@@ -8361,23 +8361,12 @@ void SetDecFloatTrapsNode::execute(thread_db* tdbb, dsql_req* /*request*/, jrd_t
 //--------------------
 
 
-void CoercionRule::setRule(TypeClause* from, TypeClause *to)
-{
-	static const USHORT FROM_MASK = FLD_has_len | FLD_has_chset | FLD_has_scale;
-	static const USHORT TO_MASK = FLD_has_len | FLD_has_chset | FLD_has_scale | FLD_legacy;
-
-	fromMask = from->flags & FROM_MASK;
-	DsqlDescMaker::fromField(&fromDsc, from);
-
-	toMask = to->flags & TO_MASK;
-	DsqlDescMaker::fromField(&toDsc, to);
-}
-
-
 SessionManagementNode* SetBindNode::dsqlPass(DsqlCompilerScratch* dsqlScratch)
 {
+	static const USHORT NON_FIELD_MASK = FLD_legacy | FLD_native;
+
 	from->resolve(dsqlScratch);
-	if (!(to->flags & FLD_legacy))
+	if (!(to->flags & NON_FIELD_MASK))
 		to->resolve(dsqlScratch);
 
 	return SessionManagementNode::dsqlPass(dsqlScratch);

src/dsql/dsql.h

@@ -329,7 +329,8 @@ enum fld_flags_vals {
 	FLD_has_len		= 16,
 	FLD_has_chset	= 32,
 	FLD_has_scale	= 64,
-	FLD_legacy		= 128
+	FLD_legacy		= 128,
+	FLD_native		= 256
 };
 
 //! Stored Procedure block

src/dsql/parse.y

@@ -5287,8 +5287,8 @@ set_decfloat_traps
 set_bind
 	: SET BIND OF set_bind_from
 			{ $$ = newNode<SetBindNode>(); $$->from = $4; }
-		TO set_bind_to
+		set_bind_to
-			{ $$ = $5; $$->to = $7; }
+			{ $$ = $5; $$->to = $6; }
 	;
 
 %type <legacyField> set_bind_from
@@ -5298,15 +5298,20 @@ set_bind_from
 
 %type <legacyField> set_bind_to
 set_bind_to
-	: simple_type
+	: TO simple_type
 		{
-			$$ = $1;
+			$$ = $2;
 		}
-	| LEGACY
+	| TO LEGACY
 		{
 			$$ = newNode<dsql_fld>();
 			$$->flags = FLD_legacy;
 		}
+	| NATIVE
+		{
+			$$ = newNode<dsql_fld>();
+			$$->flags = FLD_native;
+		}
 	;
 
 %type decfloat_traps_list_opt(<setDecFloatTrapsNode>)

src/jrd/Coercion.cpp

@@ -29,11 +29,15 @@
 #include "../jrd/Coercion.h"
 
 #include "../dsql/dsql.h"
+#include "../dsql/make_proto.h"
 #include "../jrd/align.h"
 
 using namespace Jrd;
 using namespace Firebird;
 
+static const USHORT FROM_MASK = FLD_has_len | FLD_has_chset | FLD_has_scale;
+static const USHORT TO_MASK = FLD_has_len | FLD_has_chset | FLD_has_scale | FLD_legacy | FLD_native;
+
 bool CoercionArray::coerce(dsc* d) const
 {
 	// move down through array to ensure correct order: newer rule overrides older one
@@ -46,7 +50,16 @@ bool CoercionArray::coerce(dsc* d) const
 	return false;
 }
 
-bool CoercionRule::coerce(dsc* d) const
+void CoercionRule::setRule(TypeClause* from, TypeClause *to)
+{
+	fromMask = from->flags & FROM_MASK;
+	DsqlDescMaker::fromField(&fromDsc, from);
+
+	toMask = to->flags & TO_MASK;
+	DsqlDescMaker::fromField(&toDsc, to);
+}
+
+bool CoercionRule::match(dsc* d) const
 {
 	bool found = false;
 
@@ -75,14 +88,24 @@ bool CoercionRule::coerce(dsc* d) const
 		}
 	}
 
-	if (!found)
+	return found;
+}
+
+bool CoercionRule::coerce(dsc* d) const
+{
+	// check does descriptor match FROM clause
+	if (! match(d))
 		return false;
 
-	// now define output descriptor
+	// native binding - do not touch descriptor at all
-	// first of all process LEGACY case
+	if (toMask & FLD_native)
+		return true;
+
+	// process legacy case
 	if (toMask & FLD_legacy)
 	{
-		found = true;
+		bool found = true;
+
 		switch(d->dsc_dtype)
 		{
 		case dtype_dec64:

src/jrd/Coercion.h

@@ -50,6 +50,7 @@ public:
 
 	void setRule(TypeClause* from, TypeClause *to);
 	bool coerce(dsc* d) const;
+	bool match(dsc* d) const;
 
 private:
 	dsc fromDsc, toDsc;