Add transforms feature

This provides a mechanism for specifying conversions between SQL data
types and procedural languages.  As examples, there are transforms
for hstore and ltree for PL/Perl and PL/Python.

reviews by Pavel Stěhule and Andres Freund

src/backend/commands/dropcmds.c

@@ -366,6 +366,14 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				}
 			}
 			break;
+		case OBJECT_TRANSFORM:
+			if (!type_in_list_does_not_exist_skipping(objname, &msg, &name))
+			{
+				msg = gettext_noop("transform for type %s language %s does not exist, skipping");
+				name = TypeNameToString((TypeName *) linitial(objname));
+				args = (char *) linitial(objargs);
+			}
+			break;
 		case OBJECT_TRIGGER:
 			if (!owningrel_does_not_exist_skipping(objname, &msg, &name))
 			{

src/backend/commands/event_trigger.c

@@ -98,6 +98,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SERVER", true},
 	{"TABLE", true},
 	{"TABLESPACE", false},
+	{"TRANSFORM", true},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
 	{"TEXT SEARCH DICTIONARY", true},
@@ -1090,6 +1091,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TRANSFORM:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1137,6 +1139,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_REWRITE:
 		case OCLASS_TRIGGER:
 		case OCLASS_SCHEMA:
+		case OCLASS_TRANSFORM:
 		case OCLASS_TSPARSER:
 		case OCLASS_TSDICT:
 		case OCLASS_TSTEMPLATE:

src/backend/commands/functioncmds.c

@@ -45,6 +45,7 @@
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_proc_fn.h"
+#include "catalog/pg_transform.h"
 #include "catalog/pg_type.h"
 #include "catalog/pg_type_fn.h"
 #include "commands/alter.h"
@@ -583,6 +584,7 @@ static void
 compute_attributes_sql_style(List *options,
 							 List **as,
 							 char **language,
+							 Node **transform,
 							 bool *windowfunc_p,
 							 char *volatility_p,
 							 bool *strict_p,
@@ -595,6 +597,7 @@ compute_attributes_sql_style(List *options,
 	ListCell   *option;
 	DefElem    *as_item = NULL;
 	DefElem    *language_item = NULL;
+	DefElem    *transform_item = NULL;
 	DefElem    *windowfunc_item = NULL;
 	DefElem    *volatility_item = NULL;
 	DefElem    *strict_item = NULL;
@@ -624,6 +627,14 @@ compute_attributes_sql_style(List *options,
 						 errmsg("conflicting or redundant options")));
 			language_item = defel;
 		}
+		else if (strcmp(defel->defname, "transform") == 0)
+		{
+			if (transform_item)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			transform_item = defel;
+		}
 		else if (strcmp(defel->defname, "window") == 0)
 		{
 			if (windowfunc_item)
@@ -671,6 +682,8 @@ compute_attributes_sql_style(List *options,
 	}
 
 	/* process optional items */
+	if (transform_item)
+		*transform = transform_item->arg;
 	if (windowfunc_item)
 		*windowfunc_p = intVal(windowfunc_item->arg);
 	if (volatility_item)
@@ -807,7 +820,6 @@ interpret_AS_clause(Oid languageOid, const char *languageName,
 }
 
 
-
 /*
  * CreateFunction
  *	 Execute a CREATE FUNCTION utility statement.
@@ -822,6 +834,7 @@ CreateFunction(CreateFunctionStmt *stmt, const char *queryString)
 	char	   *language;
 	Oid			languageOid;
 	Oid			languageValidator;
+	Node	   *transformDefElem = NULL;
 	char	   *funcname;
 	Oid			namespaceId;
 	AclResult	aclresult;
@@ -831,6 +844,8 @@ CreateFunction(CreateFunctionStmt *stmt, const char *queryString)
 	ArrayType  *parameterNames;
 	List	   *parameterDefaults;
 	Oid			variadicArgType;
+	List	   *trftypes_list = NIL;
+	ArrayType  *trftypes;
 	Oid			requiredResultType;
 	bool		isWindowFunc,
 				isStrict,
@@ -866,7 +881,7 @@ CreateFunction(CreateFunctionStmt *stmt, const char *queryString)
 
 	/* override attributes from explicit list */
 	compute_attributes_sql_style(stmt->options,
-								 &as_clause, &language,
+								 &as_clause, &language, &transformDefElem,
 								 &isWindowFunc, &volatility,
 								 &isStrict, &security, &isLeakProof,
 								 &proconfig, &procost, &prorows);
@@ -915,6 +930,23 @@ CreateFunction(CreateFunctionStmt *stmt, const char *queryString)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("only superuser can define a leakproof function")));
 
+	if (transformDefElem)
+	{
+		ListCell *lc;
+
+		Assert(IsA(transformDefElem, List));
+
+		foreach (lc, (List *) transformDefElem)
+		{
+			Oid typeid = typenameTypeId(NULL, lfirst(lc));
+			Oid elt = get_base_element_type(typeid);
+			typeid = elt ? elt : typeid;
+
+			get_transform_oid(typeid, languageOid, false);
+			trftypes_list = lappend_oid(trftypes_list, typeid);
+		}
+	}
+
 	/*
 	 * Convert remaining parameters of CREATE to form wanted by
 	 * ProcedureCreate.
@@ -958,6 +990,25 @@ CreateFunction(CreateFunctionStmt *stmt, const char *queryString)
 		returnsSet = false;
 	}
 
+	if (list_length(trftypes_list) > 0)
+	{
+		ListCell *lc;
+		Datum *arr;
+		int i;
+
+		arr = palloc(list_length(trftypes_list) * sizeof(Datum));
+		i = 0;
+		foreach (lc, trftypes_list)
+			arr[i++] = ObjectIdGetDatum(lfirst_oid(lc));
+		trftypes = construct_array(arr, list_length(trftypes_list),
+								   OIDOID, sizeof(Oid), true, 'i');
+	}
+	else
+	{
+		/* store SQL NULL instead of emtpy array */
+		trftypes = NULL;
+	}
+
 	compute_attributes_with_style(stmt->withClause, &isStrict, &volatility);
 
 	interpret_AS_clause(languageOid, language, funcname, as_clause,
@@ -1014,6 +1065,7 @@ CreateFunction(CreateFunctionStmt *stmt, const char *queryString)
 						   PointerGetDatum(parameterModes),
 						   PointerGetDatum(parameterNames),
 						   parameterDefaults,
+						   PointerGetDatum(trftypes),
 						   PointerGetDatum(proconfig),
 						   procost,
 						   prorows);
@@ -1653,6 +1705,293 @@ DropCastById(Oid castOid)
 	heap_close(relation, RowExclusiveLock);
 }
 
+
+static void
+check_transform_function(Form_pg_proc procstruct)
+{
+	if (procstruct->provolatile == PROVOLATILE_VOLATILE)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("transform function must not be volatile")));
+	if (procstruct->proisagg)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("transform function must not be an aggregate function")));
+	if (procstruct->proiswindow)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("transform function must not be a window function")));
+	if (procstruct->proretset)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("transform function must not return a set")));
+	if (procstruct->pronargs != 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("transform function must take one argument")));
+	if (procstruct->proargtypes.values[0] != INTERNALOID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("first argument of transform function must be type \"internal\"")));
+}
+
+
+/*
+ * CREATE TRANSFORM
+ */
+Oid
+CreateTransform(CreateTransformStmt *stmt)
+{
+	Oid			typeid;
+	char		typtype;
+	Oid			langid;
+	Oid			fromsqlfuncid;
+	Oid			tosqlfuncid;
+	AclResult	aclresult;
+	Form_pg_proc procstruct;
+	Datum		values[Natts_pg_transform];
+	bool		nulls[Natts_pg_transform];
+	bool		replaces[Natts_pg_transform];
+	Oid			transformid;
+	HeapTuple	tuple;
+	HeapTuple	newtuple;
+	Relation	relation;
+	ObjectAddress myself,
+				referenced;
+	bool		is_replace;
+
+	/*
+	 * Get the type
+	 */
+	typeid = typenameTypeId(NULL, stmt->type_name);
+	typtype = get_typtype(typeid);
+
+	if (typtype == TYPTYPE_PSEUDO)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("data type %s is a pseudo-type",
+						TypeNameToString(stmt->type_name))));
+
+	if (typtype == TYPTYPE_DOMAIN)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("data type %s is a domain",
+						TypeNameToString(stmt->type_name))));
+
+	if (!pg_type_ownercheck(typeid, GetUserId()))
+		aclcheck_error_type(ACLCHECK_NOT_OWNER, typeid);
+
+	aclresult = pg_type_aclcheck(typeid, GetUserId(), ACL_USAGE);
+	if (aclresult != ACLCHECK_OK)
+		aclcheck_error_type(aclresult, typeid);
+
+	/*
+	 * Get the language
+	 */
+	langid = get_language_oid(stmt->lang, false);
+
+	aclresult = pg_language_aclcheck(langid, GetUserId(), ACL_USAGE);
+	if (aclresult != ACLCHECK_OK)
+		aclcheck_error(aclresult, ACL_KIND_LANGUAGE, stmt->lang);
+
+	/*
+	 * Get the functions
+	 */
+	if (stmt->fromsql)
+	{
+		fromsqlfuncid = LookupFuncNameTypeNames(stmt->fromsql->funcname, stmt->fromsql->funcargs, false);
+
+		if (!pg_proc_ownercheck(fromsqlfuncid, GetUserId()))
+			aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_PROC, NameListToString(stmt->fromsql->funcname));
+
+		aclresult = pg_proc_aclcheck(fromsqlfuncid, GetUserId(), ACL_EXECUTE);
+		if (aclresult != ACLCHECK_OK)
+			aclcheck_error(aclresult, ACL_KIND_PROC, NameListToString(stmt->fromsql->funcname));
+
+		tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(fromsqlfuncid));
+		if (!HeapTupleIsValid(tuple))
+			elog(ERROR, "cache lookup failed for function %u", fromsqlfuncid);
+		procstruct = (Form_pg_proc) GETSTRUCT(tuple);
+		if (procstruct->prorettype != INTERNALOID)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("return data type of FROM SQL function must be \"internal\"")));
+		check_transform_function(procstruct);
+		ReleaseSysCache(tuple);
+	}
+	else
+		fromsqlfuncid = InvalidOid;
+
+	if (stmt->tosql)
+	{
+		tosqlfuncid = LookupFuncNameTypeNames(stmt->tosql->funcname, stmt->tosql->funcargs, false);
+
+		if (!pg_proc_ownercheck(tosqlfuncid, GetUserId()))
+			aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_PROC, NameListToString(stmt->tosql->funcname));
+
+		aclresult = pg_proc_aclcheck(tosqlfuncid, GetUserId(), ACL_EXECUTE);
+		if (aclresult != ACLCHECK_OK)
+			aclcheck_error(aclresult, ACL_KIND_PROC, NameListToString(stmt->tosql->funcname));
+
+		tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(tosqlfuncid));
+		if (!HeapTupleIsValid(tuple))
+			elog(ERROR, "cache lookup failed for function %u", tosqlfuncid);
+		procstruct = (Form_pg_proc) GETSTRUCT(tuple);
+		if (procstruct->prorettype != typeid)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("return data type of TO SQL function must be the transform data type")));
+		check_transform_function(procstruct);
+		ReleaseSysCache(tuple);
+	}
+	else
+		tosqlfuncid = InvalidOid;
+
+	/*
+	 * Ready to go
+	 */
+	values[Anum_pg_transform_trftype - 1] = ObjectIdGetDatum(typeid);
+	values[Anum_pg_transform_trflang - 1] = ObjectIdGetDatum(langid);
+	values[Anum_pg_transform_trffromsql - 1] = ObjectIdGetDatum(fromsqlfuncid);
+	values[Anum_pg_transform_trftosql - 1] = ObjectIdGetDatum(tosqlfuncid);
+
+	MemSet(nulls, false, sizeof(nulls));
+
+	relation = heap_open(TransformRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache2(TRFTYPELANG,
+							ObjectIdGetDatum(typeid),
+							ObjectIdGetDatum(langid));
+	if (HeapTupleIsValid(tuple))
+	{
+		if (!stmt->replace)
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("transform for type %s language %s already exists",
+							format_type_be(typeid),
+							stmt->lang)));
+
+		MemSet(replaces, false, sizeof(replaces));
+		replaces[Anum_pg_transform_trffromsql - 1] = true;
+		replaces[Anum_pg_transform_trftosql - 1] = true;
+
+		newtuple = heap_modify_tuple(tuple, RelationGetDescr(relation), values, nulls, replaces);
+		simple_heap_update(relation, &newtuple->t_self, newtuple);
+
+		transformid = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+		is_replace = true;
+	}
+	else
+	{
+		newtuple = heap_form_tuple(RelationGetDescr(relation), values, nulls);
+		transformid = simple_heap_insert(relation, newtuple);
+		is_replace = false;
+	}
+
+	CatalogUpdateIndexes(relation, newtuple);
+
+	if (is_replace)
+		deleteDependencyRecordsFor(TransformRelationId, transformid, true);
+
+	/* make dependency entries */
+	myself.classId = TransformRelationId;
+	myself.objectId = transformid;
+	myself.objectSubId = 0;
+
+	/* dependency on language */
+	referenced.classId = LanguageRelationId;
+	referenced.objectId = langid;
+	referenced.objectSubId = 0;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	/* dependency on type */
+	referenced.classId = TypeRelationId;
+	referenced.objectId = typeid;
+	referenced.objectSubId = 0;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	/* dependencies on functions */
+	if (OidIsValid(fromsqlfuncid))
+	{
+		referenced.classId = ProcedureRelationId;
+		referenced.objectId = fromsqlfuncid;
+		referenced.objectSubId = 0;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+	if (OidIsValid(tosqlfuncid))
+	{
+		referenced.classId = ProcedureRelationId;
+		referenced.objectId = tosqlfuncid;
+		referenced.objectSubId = 0;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, is_replace);
+
+	/* Post creation hook for new transform */
+	InvokeObjectPostCreateHook(TransformRelationId, transformid, 0);
+
+	heap_freetuple(newtuple);
+
+	heap_close(relation, RowExclusiveLock);
+
+	return transformid;
+}
+
+
+/*
+ * get_transform_oid - given type OID and language OID, look up a transform OID
+ *
+ * If missing_ok is false, throw an error if the transform is not found.  If
+ * true, just return InvalidOid.
+ */
+Oid
+get_transform_oid(Oid type_id, Oid lang_id, bool missing_ok)
+{
+	Oid			oid;
+
+	oid = GetSysCacheOid2(TRFTYPELANG,
+						  ObjectIdGetDatum(type_id),
+						  ObjectIdGetDatum(lang_id));
+	if (!OidIsValid(oid) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("transform for type %s language \"%s\" does not exist",
+						format_type_be(type_id),
+						get_language_name(lang_id, false))));
+	return oid;
+}
+
+
+void
+DropTransformById(Oid transformOid)
+{
+	Relation	relation;
+	ScanKeyData scankey;
+	SysScanDesc scan;
+	HeapTuple	tuple;
+
+	relation = heap_open(TransformRelationId, RowExclusiveLock);
+
+	ScanKeyInit(&scankey,
+				ObjectIdAttributeNumber,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(transformOid));
+	scan = systable_beginscan(relation, TransformOidIndexId, true,
+							  NULL, 1, &scankey);
+
+	tuple = systable_getnext(scan);
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "could not find tuple for transform %u", transformOid);
+	simple_heap_delete(relation, &tuple->t_self);
+
+	systable_endscan(scan);
+	heap_close(relation, RowExclusiveLock);
+}
+
+
 /*
  * Subroutine for ALTER FUNCTION/AGGREGATE SET SCHEMA/RENAME
  *

src/backend/commands/proclang.c

@@ -141,6 +141,7 @@ CreateProceduralLanguage(CreatePLangStmt *stmt)
 									  PointerGetDatum(NULL),
 									  NIL,
 									  PointerGetDatum(NULL),
+									  PointerGetDatum(NULL),
 									  1,
 									  0);
 			handlerOid = tmpAddr.objectId;
@@ -179,6 +180,7 @@ CreateProceduralLanguage(CreatePLangStmt *stmt)
 										  PointerGetDatum(NULL),
 										  NIL,
 										  PointerGetDatum(NULL),
+										  PointerGetDatum(NULL),
 										  1,
 										  0);
 				inlineOid = tmpAddr.objectId;
@@ -220,6 +222,7 @@ CreateProceduralLanguage(CreatePLangStmt *stmt)
 										  PointerGetDatum(NULL),
 										  NIL,
 										  PointerGetDatum(NULL),
+										  PointerGetDatum(NULL),
 										  1,
 										  0);
 				valOid = tmpAddr.objectId;

src/backend/commands/typecmds.c

@@ -1616,6 +1616,7 @@ makeRangeConstructors(const char *name, Oid namespace,
 								 PointerGetDatum(NULL), /* parameterModes */
 								 PointerGetDatum(NULL), /* parameterNames */
 								 NIL,	/* parameterDefaults */
+								 PointerGetDatum(NULL),		/* trftypes */
 								 PointerGetDatum(NULL), /* proconfig */
 								 1.0,	/* procost */
 								 0.0);	/* prorows */