Adding literal_column to Flask-SQLAlchemy query

Question

I'm trying to add some scalar value column to the selection that uses Flask-SQLAlchemy pagination functionality. Currently i have:

records = Item.query.paginate(1, 3, False).items

How do i have to edit this code to add column that contains total number of pages (and ideally one more column with total records number)?

pjcunningham · Accepted Answer · 2016-01-10 16:04:14Z

1

You could try passing passing a dictionary to json.dumps:

paginated = Item.query.paginate(1, 3, False)
results = {
    "records": paginated.items,
    "num_pages": paginated.pages,
    "total_count": paginated.total   
}

return json.dumps(results, cls=AlchemyEncoder)

answered Jan 10, 2016 at 16:04

pjcunningham

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jumbopap · Accepted Answer · 2016-01-09 19:35:22Z

0

paginate returns a Pagination object which contains attributes like pages, and total. See the API.

paginated = Item.query.paginate(1, 3, False)
num_pages = paginated.pages # gives you total number of pages
total_count = paginated.total

edited Jan 9, 2016 at 19:35

answered Jan 8, 2016 at 16:45

jumbopap

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3 Comments

AlexMe Over a year ago

Sorry for the confusion, but the main question is "How to add literal_column() (with the value of num_pages and/or total_count) to the resulting QuerySet?"

jumbopap Over a year ago

Why do you need this as a separate column? The paginate function already returns the number of pages in the query set.

AlexMe Over a year ago

My code returns (return json.dumps(records, cls=AlchemyEncoder)) json representation of a paginate().items query set, and i want num_pages&total_count to be a part of this json data, so that i could return all info (db rows + a couple of summary values) within a single http response.

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