Add function is_valid_label_name (#1911) (#1912)

Added the function is_valid_label_name (#1911) per user request.

This function will return a boolean value for any agtype string
passed, depending on whether it is a valid name for a label. For
all other types, not an agtype string, it will error out. Depending
on user requirements, this could be changed in the future.

Added regression tests.

regress/expected/name_validation.out

@@ -369,6 +369,33 @@ SELECT * from cypher('graph123', $$ CREATE (:A)-[:`mylabel2`]->(:C) $$) as (a ag
 ---
 (0 rows)
 
+-- user label validation
+-- invalid
+SELECT * from cypher('graph123', $$ return is_valid_label_name('1label') $$) as (result agtype);
+ result 
+--------
+ false
+(1 row)
+
+SELECT * from cypher('graph123', $$ return is_valid_label_name('2label') $$) as (result agtype);
+ result 
+--------
+ false
+(1 row)
+
+-- valid
+SELECT * from cypher('graph123', $$ return is_valid_label_name('label1') $$) as (result agtype);
+ result 
+--------
+ true
+(1 row)
+
+SELECT * from cypher('graph123', $$ return is_valid_label_name('label2') $$) as (result agtype);
+ result 
+--------
+ true
+(1 row)
+
 -- clean up
 SELECT drop_graph('graph123', true);
 NOTICE:  drop cascades to 18 other objects

regress/sql/name_validation.sql

@@ -145,6 +145,14 @@ SELECT * from cypher('graph123', $$ CREATE (:A)-[:`my&label2`]->(:C) $$) as (a a
 SELECT * from cypher('graph123', $$ CREATE (a:`mylabel`) $$) as (a agtype);
 SELECT * from cypher('graph123', $$ CREATE (:A)-[:`mylabel2`]->(:C) $$) as (a agtype);
 
+-- user label validation
+-- invalid
+SELECT * from cypher('graph123', $$ return is_valid_label_name('1label') $$) as (result agtype);
+SELECT * from cypher('graph123', $$ return is_valid_label_name('2label') $$) as (result agtype);
+-- valid
+SELECT * from cypher('graph123', $$ return is_valid_label_name('label1') $$) as (result agtype);
+SELECT * from cypher('graph123', $$ return is_valid_label_name('label2') $$) as (result agtype);
+
 -- clean up
 SELECT drop_graph('graph123', true);
 

sql/agtype_string.sql

@@ -51,3 +51,10 @@ CREATE FUNCTION ag_catalog.age_eq_tilde(agtype, agtype)
     STABLE
 PARALLEL SAFE
 AS 'MODULE_PATHNAME';
+
+CREATE FUNCTION ag_catalog.age_is_valid_label_name(agtype)
+    RETURNS boolean
+    LANGUAGE c
+    IMMUTABLE
+PARALLEL SAFE
+AS 'MODULE_PATHNAME';

src/backend/commands/label_commands.c

@@ -80,7 +80,52 @@ static void range_var_callback_for_remove_relation(const RangeVar *rel,
                                                    Oid odl_rel_oid,
                                                    void *arg);
 
+PG_FUNCTION_INFO_V1(age_is_valid_label_name);
 
+Datum age_is_valid_label_name(PG_FUNCTION_ARGS)
+{
+    agtype *agt_arg = NULL;
+    agtype_value *agtv_value = NULL;
+    char *label_name = NULL;
+    bool is_valid = false;
+
+    if (PG_ARGISNULL(0))
+    {
+        ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                errmsg("label name must not be NULL")));
+    }
+
+    agt_arg = AG_GET_ARG_AGTYPE_P(0);
+
+    if (!AGT_ROOT_IS_SCALAR(agt_arg))
+    {
+        ereport(ERROR,
+                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                 errmsg("is_valid_label_name() only supports scalar arguments")));
+    }
+
+    agtv_value = get_ith_agtype_value_from_container(&agt_arg->root, 0);
+
+    if (agtv_value->type != AGTV_STRING)
+    {
+        ereport(ERROR,
+                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                 errmsg("is_valid_label_name() only supports string arguments")));
+    }
+
+    label_name = pnstrdup(agtv_value->val.string.val,
+                          agtv_value->val.string.len);
+
+    is_valid = is_valid_label(label_name, 0);
+    pfree(label_name);
+
+    if (is_valid)
+    {
+        PG_RETURN_BOOL(true);
+    }
+
+    PG_RETURN_BOOL(false);
+}
 
 PG_FUNCTION_INFO_V1(create_vlabel);