Bigquery named parameters regex in Java - google-bigquery

Question

I am looking for a way to use a regex as value in a named parameter in the Java SDK. According to the documentation, there is no datatype for that, and using a String parameter does not work.
Is there any way to use a regex as value in a named parameter?
QueryParameterValue Class has no datatype for that:
https://googleapis.dev/java/google-cloud-clients/0.91.0-alpha/com/google/cloud/bigquery/QueryParameterValue.html#of-T-com.google.cloud.bigquery.StandardSQLTypeName-
A regex in the query would e.g. look like this:
REGEXP_CONTAINS(some_attribute, r"^any\sregex\ssearchstring$")
and should be replaced by a named parameter like:
REGEXP_CONTAINS(some_attribute, #named_regex_parameter)
I tried different syntax in the query like
REGEXP_CONTAINS(some_attribute, r#named_regex_parameter)
etc. but none of them worked. The #named_regex_parameter is of type String. I tried to use values in the form of r"regex_expression" and just the regex_expression in the parameter value.
Seems like I need to build the query String without a named parameter for the regex part. Any hints to solve this with parameters would be really appreciated!
//Edit: added code example how the named parameters are used in the query config
QueryJobConfiguration queryConfig = QueryJobConfiguration.newBuilder(query)
.setDestinationTable(TableId.of(destinationDataset, destinationTable))
.setAllowLargeResults(true)
.setCreateDisposition(CreateDisposition.CREATE_IF_NEEDED)
.setTimePartitioning(partitioning)
.setWriteDisposition(WriteDisposition.WRITE_APPEND)
.setParameterMode("NAMED")
.addNamedParameter("regexExpressionParam", QueryParameterValue.string(someRegexExpressionStringVariable)) //this does not work
.addNamedParameter("someStringParam", QueryParameterValue.string(stringVariable))
.setPriority(Priority.BATCH)
.build();
The query should use the parameter #regexExpressionParam like so:
REGEXP_CONTAINS(theAttributeToQuery, #regexExpressionParam))

Answer 1

You need to pass the regular expression string without r'...'
I had a very similar problem with running parameterized queries on Python: it was something like this.
from google.cloud import bigquery
regex_input = "^begin_word.*end_here$"
# Construct a BigQuery client object.
client = bigquery.Client()
query = """
SELECT word, word_count
FROM `bigquery-public-data.samples.shakespeare`
WHERE REGEXP_CONTAINS(word, #regex)
ORDER BY word_count DESC;
"""
job_config = bigquery.QueryJobConfig(
query_parameters=[
bigquery.ScalarQueryParameter("regex", "STRING", f"r'{regex_input}'"),
]
)
query_job = client.query(query, job_config=job_config)
At first, I thought the input had to be wrapped by r'...'; just like how I normally write a regex on BQ explorer.
I tried to modify the string input to make it like a regular expression, which was this pard f"r'{regex_input}'" of the code.
but apparently BQ correctly escapes string without our help and I can just pass down the regex string like bigquery.ScalarQueryParameter("regex", "STRING", regex_input)