Grabbing Newest Records From Duplicates

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От Travis Whitton
Тема Grabbing Newest Records From Duplicates
Дата
Msg-id cf9b4f3e0703160828s2cc0b9v6c01db6e8634e37e@mail.gmail.com
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Ответы Re: Grabbing Newest Records From Duplicates
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Given the following test table, I want to grab only the newest record and disregard any older duplicates based on name.
Isthis the most efficient way to do it? Will the indicies even make a difference? The table below demonstrates a simple
proofof concept. My final table will have millions of records; however, the test I'm doing now does not seem to use the
indicies(probably because there are too few records?). <br /><br />optin=# \d test<br />     Table "public.test"<br
/> Column|  Type   | Modifiers<br />--------+---------+-----------<br /> name   | text    |<br /> time   | date    |<br
/> id    | integer |<br />Indexes:<br />    "idx_name" btree (name) <br />    "idx_time" btree ("time")<br /><br
/>optin=#explain select * from test t1 where not exists (select 1 from test t2 where <a
href="http://t2.name">t2.name</a>= <a href="http://t1.name">t1.name</a> and t2.time > t1.time);<br /><br
/>Thanks,<br/>Travis<br /><br /> 

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