[age] 01/08: Added some comments for create_graph function (#582)

[jg...@apache.org]

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jgemignani pushed a commit to branch PG12
in repository https://gitbox.apache.org/repos/asf/age.git

commit f73b16f49154eade505539d2c0043859e2ec5757
Author: Hrishikesh Mallick <65...@users.noreply.github.com>
AuthorDate: Mon Jan 23 22:45:44 2023 +0530

    Added some comments for create_graph function (#582)
    
    * Added comments for create_graph function
---
 src/backend/commands/graph_commands.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/backend/commands/graph_commands.c b/src/backend/commands/graph_commands.c
index 095c6ad..7df40b9 100644
--- a/src/backend/commands/graph_commands.c
+++ b/src/backend/commands/graph_commands.c
@@ -57,6 +57,7 @@ static void rename_graph(const Name graph_name, const Name new_name);
 
 PG_FUNCTION_INFO_V1(create_graph);
 
+/* function that is evoked for creating a graph */
 Datum create_graph(PG_FUNCTION_ARGS)
 {
     char *graph;
@@ -64,20 +65,26 @@ Datum create_graph(PG_FUNCTION_ARGS)
     char *graph_name_str;
     Oid nsp_id;
 
+    //if no argument is passed with the function, graph name cannot be null
     if (PG_ARGISNULL(0))
     {
         ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("graph name can not be NULL")));
     }
-    graph_name = PG_GETARG_NAME(0);
+
+    //gets graph name as function argument
+    graph_name = PG_GETARG_NAME(0);  
 
     graph_name_str = NameStr(*graph_name);
 
+    //checking if the name of the graph falls under the pre-decided graph naming conventions(regex)
     if (!is_valid_graph_name(graph_name_str))
     {
         ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("graph name is invalid")));
     }
+
+    //graph name must be unique, a graph with the same name should not exist
     if (graph_exists(graph_name_str))
     {
         ereport(ERROR,
@@ -87,7 +94,8 @@ Datum create_graph(PG_FUNCTION_ARGS)
 
     nsp_id = create_schema_for_graph(graph_name);
 
-    insert_graph(graph_name, nsp_id);
+    //inserts the graph info into the relation which has all the other existing graphs info
+    insert_graph(graph_name, nsp_id);  
 
     //Increment the Command counter before create the generic labels.
     CommandCounterIncrement();
@@ -100,7 +108,8 @@ Datum create_graph(PG_FUNCTION_ARGS)
     ereport(NOTICE,
             (errmsg("graph \"%s\" has been created", NameStr(*graph_name))));
 
-    PG_RETURN_VOID();
+    //according to postgres specification of c-language functions if function returns void this is the syntax
+    PG_RETURN_VOID(); 
 }
 
 static Oid create_schema_for_graph(const Name graph_name)