[sql] Using read_sql_query instead of read_sql #4853
Merged
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The Pandas read_sql method either reads a SQL query or a database table (we require only the former) into a DataFrame. This results in an additional query (for non-SQLite databases) to determine whether the
sql
object represents a SQL query or table name. This is unnecessary as thesql
object is always a SQL statement when called fromget_df
.This PR uses the read_sql_query method instead which merely reads the SQL query into a DataFrame thus saving us executing an unnecessary statement.
Note for context about 15% of all our Presto queries originating from PyHive represented the now obsolete query.