sqlalchemy union multiple dynamic queries - sqlalchemy

Question

I am dynamically creating raw text SQL queries as follows:
# my_items is a list of dicts.
# Each dict has keys, col_1 and col_2, with different values.
for col_values in my_items:
sql = sqlalchemy.text(
"SELECT col_1, col_2
FROM my_table WHERE col_1 = :col_1 AND col_2 = :col_2")
result = conn.execute(sql, **col_values)
However, the above is not efficient and I would like to retrieve all data once by unioning all queries:
queries = []
for col_values in my_items:
sql = sqlalchemy.text(
"SELECT col_1, col_2
FROM my_table WHERE col_1 = :col_1 AND col_2 = :col_2")
queries.append(sql)
final_sql = union(*queries) # does not work with Text objects
result = conn.execute(final_sql) # not sure how to bind params for individual items here!!
The problem is that, first, I cannot use union as it expects statements instead of text, and secondly, I do not know how to bind the respective input parameters to their queries.

Answer 1

You need to bind the parameters to the TextClause created with text and turn it into a TextualSelect.
queries = []
for col_values in my_items:
stmt = (
sqlalchemy.text(
"""
SELECT col_1, col_2
FROM my_table
WHERE col_1 = :col_1 AND col_2 = :col_2
"""
)
.bindparams(**col_values)
.columns(col_1=db.<TYPE>, col_2=db.<TYPE>)
)
queries.append(stmt)
final_stmt = union(*queries)
print(final_stmt.compile(compile_kwargs={"literal_binds": True}))
SELECT col_1, col_2
FROM my_table WHERE col_1 = 1 AND col_2 = 11
UNION ALL
SELECT col_1, col_2
FROM my_table WHERE col_1 = 3 AND col_2 = 13
UNION ALL
SELECT col_1, col_2
FROM my_table WHERE col_1 = 5 AND col_2 = 15
NB. I don't the actual data or schema, so I have not run this, let me know if there is any problem.