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[EDIT] FILE: toimpl.py

from typing import TYPE_CHECKING

from sqlalchemy import schema as sa_schema

from . import ops
from .base import Operations
from ..util.sqla_compat import _copy

if TYPE_CHECKING:
    from sqlalchemy.sql.schema import Table

@Operations.implementation_for(ops.AlterColumnOp)
def alter_column(
    operations: "Operations", operation: "ops.AlterColumnOp"
) -> None:

compiler = operations.impl.dialect.statement_compiler(
        operations.impl.dialect, None
    )

existing_type = operation.existing_type
    existing_nullable = operation.existing_nullable
    existing_server_default = operation.existing_server_default
    type_ = operation.modify_type
    column_name = operation.column_name
    table_name = operation.table_name
    schema = operation.schema
    server_default = operation.modify_server_default
    new_column_name = operation.modify_name
    nullable = operation.modify_nullable
    comment = operation.modify_comment
    existing_comment = operation.existing_comment

def _count_constraint(constraint):
        return not isinstance(constraint, sa_schema.PrimaryKeyConstraint) and (
            not constraint._create_rule or constraint._create_rule(compiler)
        )

if existing_type and type_:
        t = operations.schema_obj.table(
            table_name,
            sa_schema.Column(column_name, existing_type),
            schema=schema,
        )
        for constraint in t.constraints:
            if _count_constraint(constraint):
                operations.impl.drop_constraint(constraint)

operations.impl.alter_column(
        table_name,
        column_name,
        nullable=nullable,
        server_default=server_default,
        name=new_column_name,
        type_=type_,
        schema=schema,
        existing_type=existing_type,
        existing_server_default=existing_server_default,
        existing_nullable=existing_nullable,
        comment=comment,
        existing_comment=existing_comment,
        **operation.kw
    )

if type_:
        t = operations.schema_obj.table(
            table_name,
            operations.schema_obj.column(column_name, type_),
            schema=schema,
        )
        for constraint in t.constraints:
            if _count_constraint(constraint):
                operations.impl.add_constraint(constraint)

@Operations.implementation_for(ops.DropTableOp)
def drop_table(operations: "Operations", operation: "ops.DropTableOp") -> None:
    operations.impl.drop_table(
        operation.to_table(operations.migration_context)
    )

@Operations.implementation_for(ops.DropColumnOp)
def drop_column(
    operations: "Operations", operation: "ops.DropColumnOp"
) -> None:
    column = operation.to_column(operations.migration_context)
    operations.impl.drop_column(
        operation.table_name, column, schema=operation.schema, **operation.kw
    )

@Operations.implementation_for(ops.CreateIndexOp)
def create_index(
    operations: "Operations", operation: "ops.CreateIndexOp"
) -> None:
    idx = operation.to_index(operations.migration_context)
    operations.impl.create_index(idx)

@Operations.implementation_for(ops.DropIndexOp)
def drop_index(operations: "Operations", operation: "ops.DropIndexOp") -> None:
    operations.impl.drop_index(
        operation.to_index(operations.migration_context)
    )

@Operations.implementation_for(ops.CreateTableOp)
def create_table(
    operations: "Operations", operation: "ops.CreateTableOp"
) -> "Table":
    table = operation.to_table(operations.migration_context)
    operations.impl.create_table(table)
    return table

@Operations.implementation_for(ops.RenameTableOp)
def rename_table(
    operations: "Operations", operation: "ops.RenameTableOp"
) -> None:
    operations.impl.rename_table(
        operation.table_name, operation.new_table_name, schema=operation.schema
    )

@Operations.implementation_for(ops.CreateTableCommentOp)
def create_table_comment(
    operations: "Operations", operation: "ops.CreateTableCommentOp"
) -> None:
    table = operation.to_table(operations.migration_context)
    operations.impl.create_table_comment(table)

@Operations.implementation_for(ops.DropTableCommentOp)
def drop_table_comment(
    operations: "Operations", operation: "ops.DropTableCommentOp"
) -> None:
    table = operation.to_table(operations.migration_context)
    operations.impl.drop_table_comment(table)

@Operations.implementation_for(ops.AddColumnOp)
def add_column(operations: "Operations", operation: "ops.AddColumnOp") -> None:
    table_name = operation.table_name
    column = operation.column
    schema = operation.schema
    kw = operation.kw

if column.table is not None:
        column = _copy(column)

t = operations.schema_obj.table(table_name, column, schema=schema)
    operations.impl.add_column(table_name, column, schema=schema, **kw)

for constraint in t.constraints:
        if not isinstance(constraint, sa_schema.PrimaryKeyConstraint):
            operations.impl.add_constraint(constraint)
    for index in t.indexes:
        operations.impl.create_index(index)

with_comment = (
        operations.impl.dialect.supports_comments
        and not operations.impl.dialect.inline_comments
    )
    comment = column.comment
    if comment and with_comment:
        operations.impl.create_column_comment(column)

@Operations.implementation_for(ops.AddConstraintOp)
def create_constraint(
    operations: "Operations", operation: "ops.AddConstraintOp"
) -> None:
    operations.impl.add_constraint(
        operation.to_constraint(operations.migration_context)
    )

@Operations.implementation_for(ops.DropConstraintOp)
def drop_constraint(
    operations: "Operations", operation: "ops.DropConstraintOp"
) -> None:
    operations.impl.drop_constraint(
        operations.schema_obj.generic_constraint(
            operation.constraint_name,
            operation.table_name,
            operation.constraint_type,
            schema=operation.schema,
        )
    )

@Operations.implementation_for(ops.BulkInsertOp)
def bulk_insert(
    operations: "Operations", operation: "ops.BulkInsertOp"
) -> None:
    operations.impl.bulk_insert(  # type: ignore[union-attr]
        operation.table, operation.rows, multiinsert=operation.multiinsert
    )

@Operations.implementation_for(ops.ExecuteSQLOp)
def execute_sql(
    operations: "Operations", operation: "ops.ExecuteSQLOp"
) -> None:
    operations.migration_context.impl.execute(
        operation.sqltext, execution_options=operation.execution_options
    )

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