On Thu, Feb 7, 2019 at 2:49 PM Ian Miller <irmille...@gmail.com> wrote:
>
> The reason why I iterated over .c._all_columns was because it shows the
> references to the 2 "metadata_value" columns, whereas selectable.c only
> references 1.
so that's a sign that you need to apply labels to these columns
because they are conflicting. with select(), call
select().apply_labels() so that these two columns are prefixed with
their table name in a label.
>
> For example, selectable.c shows the following:
>
> (Pdb++) list(query.c)
> [Column('metadata_value', VARCHAR(length=255), table=<non_interval_query>),
> Column('created_at', TIMESTAMP(), table=<non_interval_query>),
> <sqlalchemy.sql.elements.ColumnClause at 0x7f15e1f6fef0; %(139731962070520
> coalesce)s>]Enter code here...
>
> selectable.c._all_columns shows the following:
>
> (Pdb++) query.c._all_columns
> [Column('metadata_value', VARCHAR(length=255), table=<non_interval_query>),
> Column('metadata_value', VARCHAR(length=255), table=<non_interval_query>),
> Column('created_at', TIMESTAMP(), table=<non_interval_query>),
> <sqlalchemy.sql.elements.ColumnClause at 0x7f15e1f6fef0; %(139731962070520
> coalesce)s>]Enter code here...
>
>
>
>
> On Thursday, February 7, 2019 at 12:53:51 PM UTC-5, Mike Bayer wrote:
>>
>> just as a note, don't access .c._all_columns, just iterate over selectable.c
>>
>> On Thu, Feb 7, 2019 at 10:45 AM Ian Miller <irmil...@gmail.com> wrote:
>> >
>> > Hello Mike,
>> >
>> > Thank you for your response! I have currently constructed the ORM
>> > implementation that you suggested in your response. Here's the code:
>> >
>> > def _rebuild_non_interval_query_for_group_by(self, session, query):
>> > from sqlalchemy import table, column, select
>> > from sqlalchemy.orm import aliased
>> > from collections import defaultdict, OrderedDict
>> >
>> > post_metadata = table(
>> > "post_metadata", column("post_id"), column("metadata_value")
>> > )
>> > campaign_metadata = table(
>> > "campaign_metadata", column("campaign_id"),
>> > column("metadata_value")
>> > )
>> > asset_metadata = table(
>> > "asset_metadata", column("asset_id"), column("metadata_value")
>> > )
>> >
>> > vw_asset = table("vw_asset", column("id"))
>> > vw_campaign = table("vw_campaign", column("id"))
>> > vw_post = table("vw_post", column("id"))
>> >
>> > METADATA_PRIMARY_TABLE_MAP = {
>> > asset_metadata.name: vw_asset,
>> > campaign_metadata.name: vw_campaign,
>> > post_metadata.name: vw_post,
>> > }
>> >
>> > METADATA_NAME_TABLE_MAP = {
>> > asset_metadata.name: asset_metadata,
>> > campaign_metadata.name: campaign_metadata,
>> > post_metadata.name: post_metadata,
>> > }
>> >
>> > primary_tables = set()
>> > metadata_columns_count = defaultdict(int)
>> > metadata_alias = OrderedDict()
>> > columns = []
>> > for c in query.c._all_columns:
>> > if c.name == "metadata_value":
>> > parent_column = list(c.base_columns)[0]
>> > table = parent_column.table
>> > primary_tables.add(METADATA_PRIMARY_TABLE_MAP[table.name])
>> > metadata_columns_count[METADATA_NAME_TABLE_MAP[table.name]] +=
>> > 1
>> > alias_number =
>> > metadata_columns_count[METADATA_NAME_TABLE_MAP[table.name]]
>> > alias_name = "{}_{}".format(table.name, alias_number)
>> > alias = aliased(parent_column.table, alias_name)
>> > metadata_alias[alias_name] = alias
>> > column = alias.c.metadata_value.label(
>> > "{}_{}_{}".format(table.name, alias_number,
>> > "metadata_value")
>> > )
>> > columns.append(column)
>> > else:
>> > columns.append(c)
>> >
>> > # start constructing query
>> > non_interval_query =
>> > session.query(*columns).select_from(*primary_tables)
>> >
>> > for alias_name, alias in metadata_alias.items():
>> > object_type =
>> > self._get_object_type_from_metadata_name(alias.original.name)
>> > non_interval_query = (
>> > non_interval_query
>> > .join(
>> > alias,
>> > getattr(alias.c, "{}_id".format(object_type)) ==
>> > METADATA_PRIMARY_TABLE_MAP[alias.original.name].c.id
>> > )
>> > )
>> >
>> > non_interval_query = non_interval_query.subquery("non_interval_query")
>> >
>> > return non_interval_query
>> >
>> >
>> >
>> > The "metadata_alias" values are [('post_metadata_1", alias),
>> > ('post_metadata_2', alias)] - the alias correspond to the post_metadata_1
>> > and post_metadata_2 alias in your example. However, when I reference these
>> > in the join, the aliased table names are not "post_metadata_1" or
>> > "post_metadata_2" - they're "post_metadata_3" and "post_metadata_4". I'm
>> > unable to figure out why there's a new join seemingly created instead of
>> > referencing the aliased tables that were passed in.
>> >
>> > Here's the query that the above generates:
>> >
>> > SELECT post_metadata_1.metadata_value AS post_metadata_1_metadata_value,
>> > post_metadata_2.metadata_value AS post_metadata_2_metadata_value,
>> > non_interval_query.created_at,
>> > non_interval_query.coalesce_1 \nFROM
>> > (SELECT post_metadata_3.metadata_value AS metadata_value,
>> > post_metadata_4.metadata_value AS metadata_value, vw_post.created_at AS
>> > created_at, coalesce(count(DISTINCT vw_post.id), :coalesce_2) AS
>> > coalesce_1 \nFROM vw_post
>> > JOIN post_metadata AS post_metadata_3 ON post_metadata_3.post_id =
>> > vw_post.id
>> > JOIN post_metadata AS post_metadata_4 ON post_metadata_4.post_id =
>> > vw_post.id \nWHERE post_metadata_3.metadata_value IN (:metadata_value_1,
>> > :metadata_value_2)
>> > AND post_metadata_4.metadata_value IN (:metadata_value_3,
>> > :metadata_value_4)
>> > AND vw_post.created_at >= :created_at_1
>> > AND vw_post.created_at <= :created_at_2
>> > AND post_metadata_3.schema_uid = :schema_uid_1
>> > AND post_metadata_3.metadata_name = :metadata_name_1
>> > AND post_metadata_4.schema_uid = :schema_uid_2
>> > AND post_metadata_4.metadata_name = :metadata_name_2
>> > AND vw_post.license_id IN (:license_id_1, :license_id_2)
>> > GROUP BY vw_post.created_at, post_metadata_3.metadata_value,
>> > post_metadata_4.metadata_value, vw_post.created_at) AS non_interval_query,
>> > vw_post
>> > JOIN post_metadata AS post_metadata_1 ON post_metadata_1.post_id =
>> > vw_post.id
>> > JOIN post_metadata AS post_metadata_2 ON post_metadata_2.post_id =
>> > vw_post.id;
>> >
>> >
>> >
>> >
>> > On Tuesday, February 5, 2019 at 11:51:25 AM UTC-5, Ian Miller wrote:
>> > Hello all -
>> >
>> > I am relatively new to using SQLAlchemy for more complex use cases. I am
>> > in the process of creating a time series query, but I am unable to
>> > reference a column by its alias at the top level of the query.
>> >
>> > This is the query that I am trying to address that SQLAlchemy is currently
>> > generating:
>> >
>> >
>> >
>> > SELECT non_interval_query.metadata_value AS
>> > non_interval_query_metadata_value,
>> > coalesce(sum(non_interval_query.coalesce_2), 0) AS coalesce_1,
>> > timestamp
>> > FROM
>> > (SELECT generate_series(date_trunc('day',
>> > date('2019-01-06T00:00:00+00:00')), date_trunc('day',
>> > date('2019-01-12T00:00:00+00:00')), '1 day') AS timestamp) AS time_series
>> > LEFT OUTER JOIN
>> > (SELECT post_metadata_1.metadata_value AS post_metadata_1_metadata_value,
>> > post_metadata_2.metadata_value AS post_metadata_2_metadata_value,
>> > vw_post.created_at AS vw_post_created_at,
>> > coalesce(count(DISTINCT vw_post.id), 0) AS coalesce_1
>> > FROM vw_post
>> > JOIN post_metadata AS post_metadata_1 ON post_metadata_1.post_id =
>> > vw_post.id
>> > JOIN post_metadata AS post_metadata_2 ON post_metadata_2.post_id =
>> > vw_post.id
>> > WHERE post_metadata_1.metadata_value IN ('<metadata_values>')
>> > AND post_metadata_2.metadata_value IN ('<metadata_value>')
>> > AND vw_post.created_at >= '2019-01-06T00:00:00+00:00'
>> > AND vw_post.created_at <= '2019-01-12T00:00:00+00:00'
>> > AND post_metadata_1.schema_uid = '<schema_uid>'
>> > AND post_metadata_1.metadata_name = '<metadata_name>'
>> > AND post_metadata_2.schema_uid = '<schema_uid>'
>> > AND post_metadata_2.metadata_name = '<metadata_name>'
>> > AND vw_post.license_id IN (<license_ids>)
>> > GROUP BY vw_post.created_at,
>> > post_metadata_1.metadata_value,
>> > post_metadata_2.metadata_value,
>> > vw_post.created_at) AS non_interval_query ON date_trunc('day',
>> > created_at) = timestamp;
>> > You'll notice that "non_interval_query.metadata_value AS
>> > non_interval_query_metadata_value" specified at the beginning of the query
>> > is ambiguous due to the 2 "metadata_value" selects in the
>> > "non_interval_query" subquery. What I'm trying to do is have 2 selects at
>> > the top level - one for
>> > "non_interval_query.post_metadata_1_metadata_value" and one for
>> > "non_interval_query.post_metadata_2_metadata_value".
>> >
>> >
>> > For reference, here is the code used to generate the above query:
>> >
>> >
>> >
>> >
>> > def apply_date_group_by(self, session, query, range_gb_params):
>> > field_name = self.db.get("column")
>> > model = self._object.get("model")
>> >
>> > if not field_name or not model:
>> > raise ValueError("Invalid date group by")
>> >
>> > gb_column = self._build_column()
>> > interval = range_gb_params.get("interval")
>> > interval_type = range_gb_params.get("interval_type")
>> >
>> > time_series = func.generate_series(
>> > func.date_trunc(interval_type,
>> > func.date(range_gb_params["start"])),
>> > func.date_trunc(interval_type, func.date(range_gb_params["end"])),
>> > interval,
>> > ).label("timestamp")
>> >
>> > ts_column = column("timestamp")
>> >
>> > time_series_query = session.query(time_series).subquery("time_series")
>> > non_interval_query = query.subquery("non_interval_query")
>> > # have to replace the original gb_column with the 'timestamp' column
>> > # in order to properly merge the dataset into the time series dataset
>> > non_gb_columns, gbs = self._prepare_non_gb_columns(
>> > ts_column, gb_column, non_interval_query.columns
>> > )
>> >
>> > # construct query with correct position passed in from
>> > `range_gb_params`
>> > query_position = range_gb_params.get("query_index_position", 0)
>> > non_gb_columns.insert(query_position, ts_column)
>> >
>> > date_gb_query = session.query(*non_gb_columns).select_from(
>> > time_series_query.outerjoin(
>> > non_interval_query,
>> > func.date_trunc(interval_type, column(field_name)) ==
>> > ts_column,
>> > )
>> > )
>> >
>> > if gbs:
>> > date_gb_query = date_gb_query.group_by(*gbs)
>> >
>> > return date_gb_query.order_by(ts_column)
>> >
>> >
>> > Any help on this would be greatly appreciated!
>> >
>> >
>> > --
>> > SQLAlchemy -
>> > The Python SQL Toolkit and Object Relational Mapper
>> >
>> > http://www.sqlalchemy.org/
>> >
>> > To post example code, please provide an MCVE: Minimal, Complete, and
>> > Verifiable Example. See http://stackoverflow.com/help/mcve for a full
>> > description.
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>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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