[YSQL] ANALYZE <multiple-tables> commits kPlain transaction while DDL transaction is active

[karthik-ramanathan-3006]

Jira Link: DB-11258

Description

From vanilla postgres comments in vacuum.c:

/*
* vacuum_rel expects to be entered with no transaction active; it will
* start and commit its own transaction.  But we are called by an SQL
* command, and so we are executing inside a transaction already. We
* commit the transaction started in PostgresMain() here, and start
* another one before exiting to match the commit waiting for us back in
* PostgresMain().
*/

Thus the vanilla PG vacuum/analyze code attempts to commit any ongoing transaction that may have been active.
In YB, we begin a DDL transaction as part of the YBTxnDdlProcessUtility before entering into the vacuuming/analyzing code flow. This leads to CommitTransaction in pg_txn_manager.cc being called which ignores any active DDL transactions.
This behavior might be unintentional and this assumption might lead to errors in the future.

To repro this issue, add the following check to pg_txn_manager.cc:

Status PgTxnManager::CommitPlainTransaction() {
+  SCHECK(!IsDdlMode(), InternalError, "Received DML txn commit with DDL txn state active");
  return FinishPlainTransaction(Commit::kTrue);
}

Run an ANALYZE command spanning multiple tables and observe the above error message:
ANALYZE <tbl1>, <tbl2>;

Issue Type

kind/bug

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