Concurrent db table indexing through alembic script

Alembic supports PostgreSQL concurrently indexes creation

def upgrade():    op.execute('COMMIT')    op.create_index('ix_1', 't1', ['col1'], postgresql_concurrently=True)

I'm not using Postgres and I am not able to test it, but it should be possible.According to:

http://docs.sqlalchemy.org/en/latest/dialects/postgresql.html

Concurrent indexes are allowed in the Postgres dialect from version 0.9.9.However, a migration script like this should work with older versions (direct SQL creation):

from alembic import op, contextfrom sqlalchemy import Table, Column, Integer, String, MetaData, ForeignKeyfrom sqlalchemy.orm import relationshipfrom sqlalchemy.sql import text# ---------- COMMONS# Base objects for SQL operations are:#     - use op = INSERT, UPDATE, DELETE#     - use connection = SELECT (and also INSERT, UPDATE, DELETE but this object has lot of logics)metadata = MetaData()connection = context.get_bind()tbl = Table('test', metadata, Column('data', Integer), Column("unique_key", String))# If you want to define a index on the current loaded schema:# idx1 = Index('test_idx1', tbl.c.data, postgresql_concurrently=True)def upgrade():    ...    queryc = \    """    CREATE INDEX CONCURRENTLY test_idx1 ON test (data, unique_key);    """    # it should be possible to create an index here (direct SQL):    connection.execute(text(queryc))    ...

Whereas concurrent indexes are allowed in Postgresql, Alembic does not support concurrent operations, only one process should be running at a time.