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fix: alter sql columns to long text #7463

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merged 5 commits into from
May 8, 2019
Merged

fix: alter sql columns to long text #7463

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c9b0b63
fix: alter sql columns to long text
khtruong May 7, 2019
52c8395
fix: handle dbs that don't require text length
khtruong May 7, 2019
da0944e
fix: 1GB limit
khtruong May 7, 2019
1439c8a
fix: only handle mysql
khtruong May 7, 2019
35d41f5
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khtruong May 7, 2019
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61 changes: 61 additions & 0 deletions superset/migrations/versions/afc69274c25a_update_sql_column_data_type_in_query_.py
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# Licensed to the Apache Software Foundation (ASF) under one
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# to you under the Apache License, Version 2.0 (the
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# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
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"""update the sql, select_sql, and executed_sql columns in the
query table to support larger text

Revision ID: afc69274c25a
Revises: e9df189e5c7e
Create Date: 2019-05-06 14:30:26.181449

"""
from alembic import op
import sqlalchemy as sa

# revision identifiers, used by Alembic.
revision = 'afc69274c25a'
down_revision = 'e9df189e5c7e'

text_len = 10 ** 9 - 1


def upgrade():
try:
# Set text length if database accepts it
with op.batch_alter_table('query') as batch_op:
batch_op.alter_column(
'sql', existing_type=sa.Text, type_=sa.Text(length=text_len))
batch_op.alter_column(
'select_sql', existing_type=sa.Text, type_=sa.Text(length=text_len))
batch_op.alter_column(
'executed_sql', existing_type=sa.Text, type_=sa.Text(length=text_len))
except:
# Many databases do not have a length on text objects
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I'd prefer having a MySQL-specific if block then a try silencing all errors

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Actually after reading https://docs.sqlalchemy.org/en/13/core/type_basics.html#sqlalchemy.types.Text I'm not sure either way. It's probably ok as is since catching a more specific exception might be hard because driver-specific...

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@DiggidyDave DiggidyDave May 7, 2019 •
edited
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I would feel uncomfortable leaving a migration in an indeterminate state thought... this is a bit ugly but since there is divergent behavior between dbs for this column type, what about:

try:
   do_upgrade(with_limit=True)
except:
  do_upgrade(with_limit=False)

# if it fails after that, ok...

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Wait, are you suggesting that if it errors out then it didn't wan't/need the migration in the first place? That makes sense to me I think.

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Yes, if it errors out, it doesn't need the migration in the first place.

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Just a thought for the record: If we get rid of the batch_alter_table, it will fail after the first one and we will skip it gracefully. I think that's what we want. Not sure we need the batch here. A failure will fail as a batch anyway. Some really weird degenerate case would be if it is a mysql db and gets through 1 or 2 then the db crashes leaving one unmigrated. But that is not a catastrophic bad state.

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I ended up making the migration script only update the query table for mysql dbs. I know that it is very specific to Lyft's situation but I felt that my original implementation was not a good solution since every db has different requirements and data storage sizes for Text columns. So I don't think it is a good idea for me to try to set an arbitrary size and I wouldn't be surprised if it messed up for some other dbs.

# so skip altering for those databases
pass


def downgrade():
try:
with op.batch_alter_table('query') as batch_op:
batch_op.alter_column(
'sql', existing_type=sa.Text(length=text_len), type_=sa.Text)
batch_op.alter_column(
'select_sql', existing_type=sa.Text(length=text_len), type_=sa.Text)
batch_op.alter_column(
'executed_sql', existing_type=sa.Text(length=text_len), type_=sa.Text)
except:
pass