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These extended statistics allow the query planner to know that the prevalence of empty topics is very different in DMs, as opposed to channel messages. The `ALTER STATISTICS` adjusts the size of the "most common value" list -- it must be large enough to include the empty-topic channel messages to be fully effective. Having this list be over-large does not carry much risk, however. The `ANALYZE zerver_message` step may be quite slow.
22 lines
788 B
Python
22 lines
788 B
Python
from django.db import migrations
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class Migration(migrations.Migration):
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atomic = False
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dependencies = [
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("zerver", "0694_remove_message_unconditional_topic_indexes"),
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]
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operations = [
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migrations.RunSQL(
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sql="CREATE STATISTICS IF NOT EXISTS zerver_message_subject_is_channel_message ON subject, is_channel_message FROM zerver_message",
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reverse_sql="DROP STATISTICS IF EXISTS zerver_message_subject_is_channel_message",
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),
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migrations.RunSQL(
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sql="ALTER STATISTICS zerver_message_subject_is_channel_message SET STATISTICS 1500",
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reverse_sql="ALTER STATISTICS zerver_message_subject_is_channel_message SET STATISTICS -1",
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),
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migrations.RunSQL("ANALYZE zerver_message"),
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]
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