def forward(migrator):
# Add a placeholder field for storing a link to a WebPageContent object
migrate(
migrator.add_column(
"searchresultcontent",
"webpagecontent_id",
ForeignKeyField(WebPageContent, null=True, to_field=WebPageContent.id),
)
)
# Move the data previously in SearchResultContent model into WebPageContent,
# and link the WebPageContent to the SearchResultContent.
# Note that because the model for SearchResultContent has already been updated beyond the
# state of the table, we have to access the 'content' and 'date' fields through the "SQL"
# class instead of a field on the model. This is also the reason that we mix both
# Query object methods and raw queries below. The models access the future field names,
# and the raw queries access the past field names.
content_records = (
SearchResultContent.select(SQL("content"), SQL("date"), SearchResult.url, SearchResultContent.id)
.join(SearchResult)
.dicts()
)
for record in content_records:
web_page_content = WebPageContent.create(content=record["content"], date=record["date"], url=record["url"])
# Normally, it's not recommended to directly insert values into queries. But I do
# it here because I think Postgres and SQLite have two different interpolating strings,
# so this is one way to write the migration to make it more portable.
# I also think there is no risk that either of these fields that I insert will
# be anything other than an integer.
SearchResultContent.raw(
"UPDATE searchresultcontent SET webpagecontent_id = "
+ str(web_page_content.id)
+ "WHERE id = "
+ str(record["id"])
).execute()
# Drop unnecessary columns from SearchResultContent model
migrate(
migrator.drop_column("searchresultcontent", "date"),
migrator.drop_column("searchresultcontent", "content"),
migrator.rename_column("searchresultcontent", "webpagecontent_id", "content_id"),
migrator.drop_not_null("searchresultcontent", "content_id"),
)
