Snowpark Migration Accelerator: SQL Embedded code¶

Note

Currently, SMA only supports the pyspark.sql function.

SMA can transform SQL code that is embedded within Python or Scala files. It processes embedded SQL code in the following file extensions:

  • Python source code files (with .py extension)

  • Scala source code files (with .scala extension)

  • Jupyter Notebook files (with .ipynb extension)

  • Databricks source files (with .python or .scala extensions)

  • Databricks Notebook archive files (with .dbc extension)

Embedded SQL Code transformation Samples¶

Supported Case¶

  • Using the spark.sql function in Python to execute SQL queries:

# Original in Spark
spark.sql("""MERGE INTO people_target pt
USING people_source ps
ON (pt.person_id1 = ps.person_id2)
WHEN NOT MATCHED BY SOURCE THEN DELETE""")
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# SMA transformation
spark.sql("""MERGE INTO people_target pt
USING (
   SELECT
      pt.person_id1
   FROM
      people_target pt
      LEFT JOIN
         people_source ps
         ON pt.person_id1 = ps.person_id2
   WHERE
      ps.person_id2 IS NULL
) s_src
ON pt.person_id1 = s_src.person_id1
WHEN MATCHED THEN
   DELETE;""")
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Unsupported Cases¶

When SMA encounters code that it cannot convert, it generates an Error, Warning, or Information (EWI) message in the output code. For more details about these messages, see EWI.

The following scenarios are not currently supported:

  • When working with SQL code, you can incorporate string variables in the following way:

query = "SELECT COUNT(COUNTRIES) FROM SALES"
dfSales = spark.sql(query)
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query = "SELECT COUNT(COUNTRIES) FROM SALES" 
#EWI: SPRKPY1077 => SQL embedded code cannot be processed. 
dfSales = spark.sql(query)
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  • Combining strings to build SQL code using simple concatenation:

base = "SELECT "
criteria_1 = " COUNT(*) "
criteria_2 = " * "
fromClause = " FROM COUNTRIES"

df1 = spark.sql(bas + criteria_1 + fromClause)
df2 = spark.sql(bas + criteria_2 + fromClause)
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base = "SELECT "
criteria_1 = " COUNT(*) "
criteria_2 = " * "
fromClause = " FROM COUNTRIES"
#EWI: SPRKPY1077 => SQL embedded code cannot be processed.

df1 = spark.sql(bas + criteria_1 + fromClause)
#EWI: SPRKPY1077 => SQL embedded code cannot be processed.
df2 = spark.sql(bas + criteria_2 + fromClause)
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  • Using string interpolation to dynamically generate SQL statements:

# Old Style interpolation
UStbl = "SALES_US"
salesUS = spark.sql("SELECT * FROM %s" % (UStbl))

# Using format function
COLtbl = "COL_SALES WHERE YEAR(saleDate) > 2023"
salesCol = spark.sql("SELECT * FROM {}".format(COLtbl))

# New Style
UKTbl = " UK_SALES_JUN_18" 
salesUk = spark.sql(f"SELECT * FROM {UKTbl}")
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# Old Style interpolation
UStbl = "SALES_US"
#EWI: SPRKPY1077 => SQL embedded code cannot be processed.
salesUS = spark.sql("SELECT * FROM %s" % (UStbl))

# Using format function
COLtbl = "COL_SALES WHERE YEAR(saleDate) > 2023"
#EWI: SPRKPY1077 => SQL embedded code cannot be processed.
salesCol = spark.sql("SELECT * FROM {}".format(COLtbl))

# New Style
UKTbl = " UK_SALES_JUN_18"
#EWI: SPRKPY1077 => SQL embedded code cannot be processed.
salesUk = spark.sql(f"SELECT * FROM {UKTbl}")
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  • Using functions that generate SQL queries dynamically:

def ByMonth(month):
    query = f"SELECT * LOGS WHERE MONTH(access_date) = {month}"
    return spark.sql(query)
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def ByMonth(month):
query = f"SELECT * LOGS WHERE MONTH(access_date) = {month}"
    #EWI: SPRKPY1077 => SQL embedded code cannot be processed.
    return spark.sql(query)
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Unsupported Cases and EWI messages¶

  • When analyzing Scala code, the error code SPRKSCL1173 indicates unsupported embedded SQL statements.

/*Scala*/
 class SparkSqlExample {
    def main(spark: SparkSession) : Unit = {
    /*EWI: SPRKSCL1173 => SQL embedded code cannot be processed.*/
    spark.sql("CREATE VIEW IF EXISTS My View AS Select * From my Table WHERE date < current_date() ")
    }
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  • When Python code contains unsupported embedded SQL statements, the error code SPRKPY1077 will be displayed.

# Python Output 
#EWI: SPRKPY1077 => SQL embedded code cannot be processed.
b = spark.sql("CREATE VIEW IF EXISTS My View AS Select * From my Table WHERE date < current_date() ")
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