在Bigquery上并行操作同一个表可能导致问题，因为同时执行多个操作可能会导致互相干扰。为了避免这种情况，在cron job之间要使用锁来同步它们的操作，确保只有一个任务在执行时才能进行删除/更新操作。

以下是使用Python实现锁同步的示例代码：

from google.cloud import bigquery

# create a BigQuery client
client = bigquery.Client()

# create a lock table
lock_table_ref = client.dataset("my_dataset").table("lock_table")
lock_table = bigquery.Table(lock_table_ref)
lock_table.schema = (
    bigquery.SchemaField("job_name", "STRING", mode="REQUIRED"),
    bigquery.SchemaField("is_locked", "BOOLEAN", mode="REQUIRED"),
)
client.create_table(lock_table)

# acquire lock
def acquire_lock(client, lock_table_ref, job_name):
    # set lock
    query_string = f"""
    UPDATE `{lock_table_ref.project}.{lock_table_ref.dataset_id}.lock_table`
    SET is_locked = TRUE
    WHERE job_name = '{job_name}' AND is_locked = FALSE;
    """
    client.query(query_string).result()

    # check lock status
    query_string = f"""
    SELECT is_locked
    FROM `{lock_table_ref.project}.{lock_table_ref.dataset_id}.lock_table`
    WHERE job_name = '{job_name}';
    """
    results = client.query(query_string).result()
    for row in results:
        if row.is_locked:
            return True
    return False

# release lock
def release_lock(client, lock_table_ref, job_name):
    query_string = f"""
    UPDATE `{lock_table_ref.project}.{lock_table_ref.dataset_id}.lock_table`
    SET is_locked = FALSE
    WHERE job_name = '{job_name}';
    """
    client.query(query_string).result()

# delete table with lock synchronization
def delete_table_with_lock(client, table_ref, job_name):
    if acquire_lock(client, lock_table_ref, job_name):
        client.delete_table(table_ref)
        release_lock(client, lock_table_ref, job_name)
    else: