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primary key and unique index - Mailing list pgsql-general

From Thomas Poty
Subject primary key and unique index
Date
Msg-id CAN_ctnhdQAe3n7NgCvHUTAb1MQzZnHoNjDSPwNThWk_b9N4wZQ@mail.gmail.com
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Responses Re: primary key and unique index  (David Rowley <david.rowley@2ndquadrant.com>)
Re: primary key and unique index  (Achilleas Mantzios <achill@matrix.gatewaynet.com>)
RE: primary key and unique index  (HORDER Phil <Phil.Horder@uk.thalesgroup.com>)
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Hi all,

I am migrating fromMySQL to Postgresql 9.6.

In MySQL a  "show create table" gives me :
 ...
  PRIMARY KEY (`ID`,`CountryCode`,`LanguageCode`),
  UNIQUE KEY `unique_my table_4` (`ID`,`CountryCode`,`LanguageCode`),
...

So, In PostgreSQL, does it make sense to create a primary key AND a unique index based on the same columns?
Is PostgreSQL smart enough to use the unique index created for the primary key.

I know PostgreSQL can be based on a unique index to create a primary key but I also know it is possible to create several indexes on the same columns with the same order.

Thanks

Thomas

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