Haskell Persistent out of sync

问题

I'm using Yesod and Persistent to make a blog (really original, eh?).

At some point, I changed my model, and Persistent said that what I was trying to do is unsafe, and that I would have to do it manually. It said:

Database migration: manual intervention required.
The following actions are considered unsafe:

    ALTER TABLE "article" DROP COLUMN "date";

So I went ahead and ran that in Postgres. In fact, I have gone ahead and dropped the table "article", and I get the error:

Migrating: CREATe TABLE "article" 
      ( "id" SERIAL PRIMARY KEY UNIQUE,
        "title" VARCHAR NOT NULL,
        "author" VARCHAR NOT NULL,
        "day" DATE NOT NULL DEFAULT DATE,
        "content" VARCHAR NOT NULL)

devel.hs: SqlError { sqlState = "42703"
                   , sqlExecStatus = FatalError
                   , sqlErrorMsg = "column \"date\" does not exist"
                   , sqlErrorDetail = ""
                   , sqlErrorHint = ""
                   }

Here is how the schema currently looks (as defined using Persistent):

-- Blog Article
Article
  title   Text
  author  Text
  day     Day default=DATE
  content MathJax

What is going on here? What do I have to do to get Postgres and Persistent back in sync?

回答1:

please change your create table code to :

    digoal=# CREATE TABLE "article" 
      ( "id" SERIAL PRIMARY KEY UNIQUE,
        "title" VARCHAR NOT NULL,
        "author" VARCHAR NOT NULL,
        "day" DATE NOT NULL DEFAULT current_date,
        "content" VARCHAR NOT NULL);
    CREATE TABLE

PostgreSQL no DATA function, so you can use current_date instead.

回答2:

I'm answering my own question because digoal's solution wasn't exactly right, but he got the main idea right, so he deserves the karma. But the real solution is too big for a comment. Basically, I did have a problem in my Persistent schema. As digoal said, Postgres does not have a 'date' function. It does have 'current_date'. So the new Persistent schema looks like:

-- Blog Article
Article
  title   Text
  author  Text
  day     Day default=CURRENT_DATE
  content MathJax

来源：https://stackoverflow.com/questions/23004528/haskell-persistent-out-of-sync

标签

postgresql

yesod