#35777: MySQL: cannot add key limited index on TEXT columns
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Reporter: Tobias Krönke | Owner: (none)
Type: Uncategorized | Status: new
Component: Migrations | Version: 5.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Tobias Krönke):
The `url__startswith='https://google.com%'` query was just an example. I
would like to optimize all `startswith` queries on that field. I've
created this crude workaround and implemented my own `Index`:
{{{
class ColumnPrefixIndex:
max_name_length = 60
contains_expressions = False
fields_orders = []
include = []
expressions = []
fields = []
def __init__(self, column, prefix, name):
self.prefix = prefix
self.column = column
self.name = name
def create_sql(self, model, schema_editor, using="", **kwargs):
table = model._meta.db_table
sql = f'CREATE INDEX {self.name} ON {table}
({self.column}({self.prefix}));'
kwargs['sql'] = sql
return schema_editor._create_index_sql(
model,
name=self.name,
using=using,
**kwargs,
)
def deconstruct(self):
kwargs = {'column': self.column, 'prefix': self.prefix, 'name':
self.name}
path = "%s.%s" % (self.__class__.__module__,
self.__class__.__name__)
return path, self.expressions, kwargs
def clone(self):
return self.__class__(self.column, self.prefix, self.name)
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/35777#comment:5>
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