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POQuery Plan of postgres with indexes
 

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    <p>I have a postgres table having the following schema</p> <pre><code> Table "public.myTable" Column | Type | Modifiers ----------- +--------------------------+----------- serial_number | character varying(255) | name | character varying(255) | Designation | character varying(255) | place | character varying(255) | timeOfJoining | timestamp with time zone | timeOfLeaving | timestamp with time zone | Indexes: "name_Designation_place" btree (name, Designation, place) "Designation_place_name" btree (Designation, place, name) "Designation_name_place" btree (Designation, name, place) "timeOfJoining_timeOfLeaving" btree (timeOfJoining, timeOfLeaving) "timeOfJoining_timeOfLeaving" btree (timeOfJoining, timeOfLeaving) </code></pre> <p>Now when I run the query of the form: </p> <pre><code>explain analyze select place from myTable where Designation='Manager' and timeOfJoining&gt;'1930-10-10'; </code></pre> <p>I am getting the following plan:</p> <pre><code>Index Scan using Designation_place_name on myTable (cost=0.00..67701.36 rows=22043 width=27) (actual time=0.061..3.796 rows=3376 loops=1) Index Cond: ((relation)::text = 'Manager'::text) Filter: (timeOfJoining &gt; '1930-10-10 00:00:00+05:53:20'::timestamp with time zone) Total runtime: 4.082 ms (4 rows) </code></pre> <p>Now I am unable to understand as to how the query plan is executed. Does the query plan first retrieve the serial_number from the index Designation_place_name on myTable and then goes to myTable and fetches the rows and then performs the filtering on timeOfJoining</p> <p>OR</p> <p>Does the query plan fetch both the indexes timeOfJoining_timeOfLeaving and Designation_place_name and then performs a join, and upon this join the filtering is done?</p>
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