[PATCH] rewriteGraphTable: Fix missing RTEs in FROM clause by setting inFromCl=true

Hi all,

I made a super simple extension `https://github.com/Z-Xiao-M/pg_pgq2sql` to get the equivalent SQL of PGQ queries – it simply calls `pg_get_querydef` after `QueryRewrite` to fetch the SQL text.

However, I noticed that some FROM clauses were missing in the generated SQL statements.

```
postgres=# SELECT * FROM pg_pgq2sql($$
SELECT common_name
FROM GRAPH_TABLE (
social_graph
MATCH (a IS users)-[]->(x IS users)<-[]-(b IS users)
WHERE a.name = 'Alice' AND b.name = 'Bob'
COLUMNS (x.name AS common_name)
)
$$);
pg_pgq2sql
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
SELECT common_name +
FROM LATERAL ( SELECT users_1.name AS common_name +
WHERE users.id = follows.follower AND users_1.id = follows.following AND users_2.id = follows_1.follower AND users_1.id = follows_1.following AND users.name::text = 'Alice'::text AND users_2.name::text = 'Bob'::text) "graph_table"
(1 row)
```

I did a quick check and found the issue: some `rte->inFromCl` were set to `false` (should be `true` here). Here’s a quick patch to fix it:

```
postgres(at)zxm-VMware-Virtual-Platform:~/code/postgres$ git diff
diff --git a/src/backend/rewrite/rewriteGraphTable.c b/src/backend/rewrite/rewriteGraphTable.c
index 06f2f3442d8..d43704ef233 100644
--- a/src/backend/rewrite/rewriteGraphTable.c
+++ b/src/backend/rewrite/rewriteGraphTable.c
@@ -498,7 +498,7 @@ generate_query_for_graph_path(RangeTblEntry *rte, List *graph_path)
*/
rel = table_open(pe->reloid, AccessShareLock);
pni = addRangeTableEntryForRelation(make_parsestate(NULL), rel, AccessShareLock,
- NULL, true, false);
+ NULL, true, true);
table_close(rel, NoLock);
path_query->rtable = lappend(path_query->rtable, pni->p_rte);
path_query->rteperminfos = lappend(path_query->rteperminfos, pni->p_perminfo);
```

After applying the patch, the FROM clause is now complete:

```
postgres=# SELECT * FROM pg_pgq2sql($$
SELECT common_name
FROM GRAPH_TABLE (
social_graph
MATCH (a IS users)-[]->(x IS users)<-[]-(b IS users)
WHERE a.name = 'Alice' AND b.name = 'Bob'
COLUMNS (x.name AS common_name)
)
$$);
pg_pgq2sql
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
SELECT common_name +
FROM LATERAL ( SELECT users_1.name AS common_name +
FROM users, +
follows, +
users users_1, +
follows follows_1, +
users users_2 +
WHERE users.id = follows.follower AND users_1.id = follows.following AND users_2.id = follows_1.follower AND users_1.id = follows_1.following AND users.name::text = 'Alice'::text AND users_2.name::text = 'Bob'::text) "graph_table"
(1 row)

postgres=#
postgres=# SELECT common_name
FROM GRAPH_TABLE (
social_graph
MATCH (a IS users)-[]->(x IS users)<-[]-(b IS users)
WHERE a.name = 'Alice' AND b.name = 'Bob'
COLUMNS (x.name AS common_name)
) ;
common_name
-------------
Charlie
(1 row)

postgres=# SELECT common_name
FROM LATERAL ( SELECT users_1.name AS common_name
FROM users,
follows,
users users_1,
follows follows_1,
users users_2
WHERE users.id = follows.follower AND users_1.id = follows.following AND users_2.id = follows_1.follower AND users_1.id = follows_1.following AND users.name::text = 'Alice'::text AND users_2.name::text = 'Bob'::text) "graph_table";
common_name
-------------
Charlie
(1 row)
```

Curious to hear your thoughts/suggestions on this.

--
regards,
Man Zeng