PostgreSQL 11 higher Planning time on Partitioned table

Question

I am looking to Range Partition one of my table (i.e. TransactionLog) in PostgreSQL 11.
While evaluating query performance between the un-partitioned and partitioned table I am getting huge difference in planning time. Planning time is very high in partitioned table.
Similarly when I query by specifying partition name directly in query the planning time is much less 0.081 ms as compared to when I query based on partition table (parent table) name in query, where planning time 6.231 ms (Samples below).

Let me know how can I improve query performance on partitioned table.

Following is the schema

CREATE TABLE TransactionLog (
    txid character varying(36) NOT NULL,
    txnDetails character varying(64),
    loggingtime timestamp(6) without time zone DEFAULT LOCALTIMESTAMP,
) PARTITION BY RANGE(loggingtime);

CREATE TABLE IF NOT EXISTS TransactionLog_20200223 PARTITION OF TransactionLog FOR VALUES FROM ('2020-02-23') TO ('2020-02-24');
CREATE UNIQUE INDEX TransactionLog_20200223_UnqTxId ON TransactionLog_20200223 (txnid);

Following is explain analyze result when I query Directly on partition. Planning time ~0.080 ms (average of 10 execution)

postgres=> EXPLAIN (ANALYZE,VERBOSE,COSTS,BUFFERS,TIMING,SUMMARY) select txnDetails FROM mra_part.TransactionLog_20200223 WHERE txnid = 'febd139d-1b7f-4564-a004-1b3474e51756';
                                                                             QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Index Scan using TransactionLog_20200223_UnqTxId on TransactionLog_20200223 (cost=0.57..4.61 rows=1 width=10) (actual time=0.039..0.040 rows=1 loops=1)
   Output: txnDetails
   Index Cond: ((TransactionLog_20200223.txnid)::text = 'febd139d-1b7f-4564-a004-1b3474e51756'::text)
   Buffers: shared hit=5
 **Planning Time: 0.081 ms**
 Execution Time: 0.056 ms
(6 rows)

Following is explain analyze result when I query by parent-table. Planning time ~6.198 ms (average of 10 execution)

postgres=> EXPLAIN (ANALYZE,VERBOSE,COSTS,BUFFERS,TIMING,SUMMARY)  select txnDetails FROM mtdauthlog WHERE txnid = 'febd139d-1b7f-4564-a004-1b3474e51756' AND loggingtime >= '2020-02-23'::timestamp without time zone AND loggingtime < '2020-02-24'::timestamp without time zone;
                                                                                              QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Append  (cost=0.57..4.62 rows=1 width=10) (actual time=0.036..0.037 rows=1 loops=1)
   Buffers: shared hit=5
   ->  Index Scan using TransactionLog_20200223_UnqTxId on TransactionLog_20200223  (cost=0.57..4.61 rows=1 width=10) (actual time=0.035..0.036 rows=1 loops=1)
         Output: TransactionLog_20200223.txnDetails
         Index Cond: ((TransactionLog_20200223.txnid)::text = 'febd139d-1b7f-4564-a004-1b3474e51756'::text)
         Filter: ((TransactionLog_20200223.loggingtime >= '2020-02-23 00:00:00'::timestamp without time zone) AND (TransactionLog_20200223.loggingtime < '2020-02-24 00:00:00'::timestamp without time zone))
         Buffers: shared hit=5
 **Planning Time: 6.231 ms**
 Execution Time: 0.076 ms
(9 rows)

PostgreSQL Version : PostgreSQL 11.7 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39), 64-bit