Write migration for removing redundant channel_id

This will:
  * fix bad db entries
  * remove channel id from conda_package_build table

conda-store-server/conda_store_server/_internal/alembic/versions/89637f546129_remove_conda_package_build_channel.py

@@ -0,0 +1,155 @@
+# Copyright (c) conda-store development team. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+"""remove conda package build channel
+
+Revision ID: 89637f546129
+Revises: bf065abf375b
+Create Date: 2024-12-04 13:09:25.562450
+
+"""
+from alembic import op, context
+from sqlalchemy import Column, INTEGER, String, ForeignKey, table, select, engine_from_config, pool
+
+# revision identifiers, used by Alembic.
+revision = '89637f546129'
+down_revision = 'bf065abf375b'
+branch_labels = None
+depends_on = None
+
+
+# This function will go thru all the conda_package_build entries and ensure
+# that the right package_id is associated with it
+def fix_misrepresented_packages(conn):
+    # conda_packages is a hash of channel-id_name_version to conda_package id
+    conda_packages = {}
+
+    conda_package_build_table = table(
+        "conda_package_build",
+        Column("id", INTEGER),
+        Column("channel_id", INTEGER),
+        Column("package_id", INTEGER, ForeignKey("conda_package.id")),
+    )
+    conda_package_table = table(
+        "conda_package",
+        Column("id", INTEGER),
+        Column("channel_id", INTEGER),
+        Column("name", String),
+        Column("version", String),
+    )
+
+    def get_conda_package_id(conn, channel_id, name, version):
+        hashed_name = f"{channel_id}-{name}-{version}"
+
+        # if package exists in the conda_packages dict, return it
+        if hashed_name in conda_packages:
+            return conda_packages[hashed_name]
+
+        # if not, then query the db for the package
+        package = conn.execute(
+            select(conda_package_table).where(
+                conda_package_table.c.channel_id == channel_id,
+                conda_package_table.c.name == name,
+                conda_package_table.c.version == version,
+            )
+        ).first()
+
+        # save the package into the conda_packages dict
+        conda_packages[hashed_name] = package.id
+        return package.id
+
+    for row in conn.execute(
+        select(
+            conda_package_build_table.c.id,
+            conda_package_build_table.c.package_id,
+            conda_package_build_table.c.channel_id,
+            conda_package_table.c.name,
+            conda_package_table.c.version
+        ).join(
+            conda_package_build_table,
+            conda_package_build_table.c.package_id == conda_package_table.c.id
+        )
+    ):
+        # the channel_id might already be empty
+        if row[2] is None:
+            continue
+
+        package_id = get_conda_package_id(conn, row[2], row[3], row[4])
+        # if found package id does not match the found package id, we'll need to updated it
+        if package_id != row[1]:
+            update_package_query = conda_package_build_table.update().where(
+                conda_package_build_table.c.id == op.inline_literal(row[0])
+            ).values(
+                {"package_id": op.inline_literal(package_id)}
+            )
+            conn.execute(update_package_query)
+            conn.commit()
+
+def upgrade():
+    target_table = "conda_package_build"
+
+    # Due to the issue fixed in https://github.com/conda-incubator/conda-store/pull/961
+    # many conda_package_build entries have the wrong package entry (but the right channel).
+    # Because the packages are duplicated, we can not recreate the _conda_package_build_uc
+    # constraint without the channel_id. 
+    # So, go thru each conda_package_build and re-associate it with the correct conda_package
+    # based on the channel id.
+    bind = op.get_bind()
+    fix_misrepresented_packages(bind)
+
+    # remove channel column from constraints
+    op.drop_constraint(
+        constraint_name="_conda_package_build_uc",
+        table_name=target_table,
+    )
+
+    # re-add the constraint without the channel column
+    op.create_unique_constraint(
+        constraint_name="_conda_package_build_uc",
+        table_name=target_table,
+        columns=[ 
+            "package_id",
+            "subdir",
+            "build",
+            "build_number",
+            "sha256",
+        ],
+    )
+
+    # remove channel column
+    op.drop_column(
+        target_table, 
+        "channel_id",
+        mssql_drop_foreign_key=True,
+    )
+
+
+def downgrade():
+    target_table = "conda_package_build"
+
+    # remove channel column from constraints
+    op.drop_constraint(
+        constraint_name="_conda_package_build_uc",
+        table_name=target_table,
+    )
+
+    # add channel column
+    op.add_column(
+        target_table,
+        Column("channel_id", INTEGER, ForeignKey("conda_channel.id"))
+    )
+
+    # re-add the constraint with the channel column
+    op.create_unique_constraint(
+        constraint_name="_conda_package_build_uc",
+        table_name=target_table,
+        columns=[ 
+            "channel_id",
+            "package_id",
+            "subdir",
+            "build",
+            "build_number",
+            "sha256",
+        ],
+    )