What indexes to add to pgsql database table?

Question

PostgreSQL

Table structure -
Number of records - from 50,000 to 100,000
Here are some queries for this table:
1).

select "start" from "channel_program" where "channel_id" = "channels"."id" and "end" < '2019-07-02 06:10:21' order by "start" desc limit 1

2).

select "start" from "channel_program" where "channel_id" = "channels"."id" and "start" <= '2019-07-02 06:10:21' and "end" > '2019-07-02 06:10:21' limit 1

3).

select "start" from "channel_program" where "channel_id" = "channels"."id" and "start" > '2019-07-02 06:10:21' limit 1

4).

select * from "channel_program" where "start"::date = '2019-07-02' and "channel_program"."channel_id" in (14) order by "start" asc

Answer 1

1. b-tree on channel_id and start seems to be successful.
2. It is worth considering the distribution of data, but this is if you understand how it affects. And so, just take yes and test your queries on a test table.
3. Do not forget to collect statistics.