Converts Oracle, SQL-Server, and other DDL to Snowflake DDL

sql2sf.py

#!/usr/bin/python
# $Id: $

# Converts Oracle, SQL-Server, and other DDL to Snowflake DDL


def usage():
    print """\
# Usage: sql2sf.py input-file [output-file]
    """

import sys
import traceback
import etl_util
import os, glob, errno
import shutil
import cStringIO, string, re
from string import maketrans
import argparse

### RegExes for Oracle dialect that Snowflake doesn't support

# VARCHAR2(n BYTE) => VARCHAR(n)
varchar2_re = re.compile('(.*)(VARCHAR2\((\d+)(\s+.+)?\))(.*)', re.IGNORECASE)

# CHAR(n BYTE) => CHAR(n)
char_re = re.compile('(.*)(CHAR\((\d+)(\s+.+)\))(.*)', re.IGNORECASE)

# DEFAULT SYSDATE => deleted (OK only because data loaded from table should already have date)
# Snowflake DEFAULT must be literal
default_sysdate_re = re.compile('(.*)\ (DEFAULT SYSDATE)\ (.*)', re.IGNORECASE)

# SYSDATE => CURRENT_TIMESTAMP()
#sysdate_re = re.compile('(.*)\ (SYSDATE)\ (.*)', re.IGNORECASE)
sysdate_re = re.compile('(.*[,\(\s])(SYSDATE)([,\)\s].*)', re.IGNORECASE)

# SEGMENT CREATION type => ignore
segment_creation_re = re.compile('(.*)\ (SEGMENT\s+CREATION\s+(?:IMMEDIATE|DEFERRED))(.*)', re.IGNORECASE)

# NOT NULL ENABLE => NOT NULL
not_null_enable_re = re.compile('(.*)(NOT\s+NULL\s+ENABLE)(.*)', re.IGNORECASE)

# find prior period, e.g. trunc(col,'MM')-1 => dateadd('MM', -1, trunc(col, 'MM'))
prior_period_re = re.compile('(.*)(TRUNC\(\s*(.+?),\s*(\'.+?\')\s*\)\s*(-?\s*\d+))(.*)', re.IGNORECASE)

# add months, e.g. add_months(trunc(col, 'MM'), -5) => dateadd(month, -5, col)
add_months_re = re.compile('(.*)(ADD_MONTHS\(\s*TRUNC\(\s*(.+?),\s*(\'.+?\')\s*\),\s*(-?\s*\d+))(.*)', re.IGNORECASE)


### RegExes for SQL-Server dialect that Snowflake doesn't support

# NULL (explicit NULL constraint) -- ignore
null_constraint_re = re.compile('(.*)((?<!NOT)\s+NULL(?!::))(.*)', re.IGNORECASE)
is_null_condition_re = re.compile('.*IS NULL.*', re.IGNORECASE)

# NVARCHAR => VARCHAR
nvarchar_re = re.compile('(.*)\ (NVARCHAR)(.*)', re.IGNORECASE)

# NVARCHAR => VARCHAR
nchar_re = re.compile('(.*)\ (NCHAR)(.*)', re.IGNORECASE)

# ON PRIMARY => ignore
on_primary_re = re.compile('(.*)\ (ON PRIMARY)(.*)', re.IGNORECASE)

# DATETIME => TIMESTAMP
datetime_re = re.compile('(.*)\ (DATETIME)(.*)', re.IGNORECASE)

# BIT => BOOLEAN
bit_re = re.compile('(.*)\ (BIT)(.*)', re.IGNORECASE)


### RegExes for Redshift dialect that Snowflake doesn't support

# DISTKEY(col) => ignore
# DISTKEY => ignore
distkey_re = re.compile('(.*)(\s*DISTKEY\s*(?:\(.*?\))?)(.*)', re.IGNORECASE)

# SORTKEY(col) => ignore
sortkey_re = re.compile('(.*)(\s*SORTKEY\s*\(.*?\))(.*)', re.IGNORECASE)

# SORTKEY => ignore through end of statement
sortkey_multiline_re = re.compile('(.*)(\s*SORTKEY\s*\(?\s*$)(.*)', re.IGNORECASE)

# ENCODE type => ignore
encode_re = re.compile('(.*)(\sENCODE\s+.+?)((?:,|\s+|$).*)', re.IGNORECASE)

# DISTSTYLE type => ignore
diststyle_re = re.compile('(.*)(\s*DISTSTYLE\s+.+?)((?:,|\s+|$).*)', re.IGNORECASE)

# 'now'::character varying => current_timestamp
now_character_varying_re = re.compile('(.*)(\'now\'::(?:character varying|text))(.*)', re.IGNORECASE)

# bpchar => char
bpchar_re = re.compile('(.*)(bpchar)(.*)', re.IGNORECASE)

# character varying => varchar
character_varying_re = re.compile('(.*)(character varying)(.*)')

# interleaved => ignore
interleaved_re = re.compile('(.*)(interleaved)(.*)', re.IGNORECASE)

# identity(start, 0, ([0-9],[0-9])::text) => identity(start, 1)
identity_re = re.compile('(.*)\s*DEFAULT\s*"identity"\(([0-9]*),.*?(?:.*?::text)\)(.*)', re.IGNORECASE)

### RegExes for Netezza dialect that Snowflake doesn't support

## casting syntax
# INT4(expr) => expr::INTEGER
int4_re = re.compile('(.*)\ (INT4\s*\((.*?)\))(.*)', re.IGNORECASE)

### RegExes for common/standard types that Snowflake doesn't support
bigint_re = re.compile('(.*)\ (BIGINT)(.*)', re.IGNORECASE)
smallint_re = re.compile('(.*)\ (SMALLINT)(.*)', re.IGNORECASE)
floatN_re = re.compile('(.*)\ (FLOAT\d+)(.*)', re.IGNORECASE)

# CREATE [type] INDEX => ignore through end of statement
index_re = re.compile('(.*)(CREATE(?:\s+(?:UNIQUE|BITMAP))?\ INDEX)(.*)', re.IGNORECASE)

# ALTER TABLE ... ADD PRIMARY KEY => ignore
pk_re = re.compile('(.*)(ALTER\s+TABLE\s+.*ADD\s+PRIMARY\s+KEY)(.*)', re.IGNORECASE)

# SET ... TO => ignore
set_re = re.compile('(.*)(SET\s+.*TO)(.*)', re.IGNORECASE)


statement_term_re = re.compile('(.*);(.*)', re.IGNORECASE)

def make_snow(sqlin, sqlout, no_comments):
    ### processing mode
    comment_lines = None
    term_re = None

    for line in sqlin:
        ### state variables
        pre = None
        clause = None
        post = None
        comment = None

        sql = line.rstrip()
        sql = sql.replace('[', '').replace(']', '')

        # print >> sys.stdout, 'input: ' + sql

        if comment_lines:
            result = term_re.match(sql)
            if result:
                comment_lines = None
                term_re = None
            sql = '-- {0}'.format(sql)

        # VARCHAR2(n BYTE) => VARCHAR(n)
        result = varchar2_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)     # varchar2 clause
            cnt = result.group(3)
            discard = result.group(4)
            post = result.group(5)
            sql = '{0}{1}({2}){3}\t\t-- {4}'.format(pre, clause[0:7], cnt, post, clause)

        # CHAR(n BYTE) => CHAR(n)
        result = char_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)     # char clause
            cnt = result.group(3)
            discard = result.group(4)
            post = result.group(5)
            sql = '{0}{1}({2}){3}\t\t-- {4}'.format(pre, clause[0:4], cnt, post, clause)

        # DEFAULT SYSDATE => deleted (OK only because data loaded from table should already have date)
        result = default_sysdate_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} {1}\t\t-- {2}'.format(pre, post, clause)

        # NVARCHAR => VARCHAR
        result = nvarchar_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} VARCHAR {1}\t\t-- {2}'.format(pre, post, clause)

        # NCHAR => CHAR
        result = nchar_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} CHAR {1}\t\t-- {2}'.format(pre, post, clause)

        # DATETIME => TIMESTAMP
        result = datetime_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} TIMESTAMP {1}\t\t-- {2}'.format(pre, post, clause)

        # BIGINT => INTEGER
        #result = bigint_re.match(sql)
        #if result:
        #    pre = result.group(1)
        #    clause = result.group(2)
        #    post = result.group(3)
        #    sql = '{0} INTEGER {1}\t\t-- {2}'.format(pre, post, clause)

        # SMALLINT => INTEGER
        #result = smallint_re.match(sql)
        #if result:
        #    pre = result.group(1)
        #    clause = result.group(2)
        #    post = result.group(3)
        #    sql = '{0} INTEGER {1}\t\t-- {2}'.format(pre, post, clause)

        # BIT => BOOLEAN
        result = bit_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} BOOLEAN {1}\t\t-- {2}'.format(pre, post, clause)

        # FLOAT8 => FLOAT
        result = floatN_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} FLOAT {1}\t\t-- {2}'.format(pre, post, clause)

        # NULL (without NOT) => implicit nullable
        result = null_constraint_re.match(sql)
        if result and is_null_condition_re.match(sql):
            # we are in query or DML, so not looking at a constraint
            result = None
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}{1}\t\t-- {2}'.format(pre, post, clause)

        # ON PRIMARY => ignore
        result = on_primary_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}{1}\t\t-- {2}'.format(pre, post, clause)

        # DISTKEY(col) => ignore
        result = distkey_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}{1}\t\t-- {2}'.format(pre, post, clause)

        # SORTKEY(col) => ignore
        result = sortkey_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}{1}\t\t-- {2}'.format(pre, post, clause)

        # SORTKEY => ignore through end of statement
        result = sortkey_multiline_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0};\n-- {2} {1}'.format(pre, post, clause)
            comment_lines = 1
            term_re = statement_term_re

        # ENCODE type => ignore
        result = encode_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}{1}\t\t-- {2}'.format(pre, post, clause)

        # DISTSTYLE type => ignore
        result = diststyle_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}{1}\t\t-- {2}'.format(pre, post, clause)

        # 'now'::(character varying|text) => current_timestamp
        result = now_character_varying_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}CURRENT_TIMESTAMP{1} --{2}'.format(pre,post,clause)

        # bpchar => char
        result = bpchar_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}char{1} --{2}'.format(pre,post,clause)

        result = character_varying_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}varchar{1}  --{2}'.format(pre,post,clause)

        # interleaved => ignore
        result = interleaved_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} {1} --{2}'.format(pre,post,clause)

        result = identity_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0} IDENTITY({1},1) {2}'.format(pre,clause,post)

        # SEGMENT CREATION type => ignore
        result = segment_creation_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0};;\n-- {2} {1}'.format(pre, post, clause)
            comment_lines = 1
            term_re = statement_term_re

        # ALTER TABLE ... ADD PRIMARY KEY => ignore
        result = index_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}-- {2} {1}'.format(pre, post, clause)
            comment_lines = 1
            term_re = statement_term_re

        # INDEX CREATION => ignore through end of statement
        result = pk_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}-- {2} {1}'.format(pre, post, clause)
            comment_lines = 1
            term_re = statement_term_re

        # SET ... TO => ignore
        result = set_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}-- {2} {1}'.format(pre, post, clause)
            comment_lines = 1
            term_re = statement_term_re

        # NOT NULL ENABLE => NOT NULL
        result = not_null_enable_re.match(sql)
        if result:
            pre = result.group(1)
            clause = result.group(2)
            post = result.group(3)
            sql = '{0}NOT NULL{1}\t\t-- {2}'.format(pre, post, clause)

        ## DML transformations that might appear multiple times per line
        dml_repeat = True
        while dml_repeat:
            dml_repeat = False

            # determine prior period
            # e.g. trunc(sysdate,'MM')-1
            result = prior_period_re.match(sql)
            if result:
                pre = result.group(1)
                clause = result.group(2)
                col = result.group(3)
                units = result.group(4)
                offset = result.group(5)
                post = result.group(6)
                sql = '{0}dateadd({4}, {5}, trunc({3}, {4}))'.format(pre, post, clause, col, units, offset)
                comment = append_comment(comment, clause, no_comments)
                dml_repeat = True

            # add_months
            # e.g. add_months(trunc(sysdate, 'MM'), -5) => dateadd('MM', -5, trunc(current_timestamp, 'MM'))
            result = add_months_re.match(sql)
            if result:
                raise Exception("Snowflake now has add_months() function -- verify can use as-is")

            # SYSDATE => CURRENT_TIMESTAMP()
            result = sysdate_re.match(sql)
            if result:
                pre = result.group(1)
                clause = result.group(2)
                post = result.group(3)
                sql = '{0} CURRENT_TIMESTAMP() {1}'.format(pre, post, clause)
                comment = append_comment(comment, clause, no_comments)
                dml_repeat = True

            # INT4(expr) => expr::INTEGER
            result = int4_re.match(sql)
            if result:
                pre = result.group(1)
                clause = result.group(2)
                col = result.group(3)
                post = result.group(4)
                sql = '{0} {3}::integer {1}'.format(pre, post, clause, col)
                comment = append_comment(comment, clause, no_comments)
                dml_repeat = True

        # write out possibly modified line
        sqlout.write(sql)
        if comment:
            sqlout.write('\t\t-- {0}'.format(comment))
        sqlout.write('\n')
        continue

def append_comment(old_comment, new_comment, no_comments):
    if no_comments:
        return None
    if old_comment and new_comment:
        return '{0} // {1}'.format(old_comment, new_comment)
    if not old_comment:
        return new_comment
    return old_comment

##### MAIN #####
if __name__ == "__main__":

    parser = argparse.ArgumentParser(description='Convert SQL dialects to Snowflake.')
    parser.add_argument('--no_comments', action='store_true',
        help='suppress comments with changes (default: show changes)')
    parser.add_argument('inputfile', action='store', nargs='?', type=argparse.FileType('r'), default=sys.stdin,
        help='input SQL file in other-vendor dialect (default: stdin)')
    parser.add_argument('outputfile', action='store', nargs='?', type=argparse.FileType('w'), default=sys.stdout,
        help='output SQL file in Snowflake dialect (default: stdout)')
    args=parser.parse_args();
    print >> sys.stderr, "no_comments = " + str(args.no_comments)
    print >> sys.stderr, "input: " + str(args.inputfile.name)
    print >> sys.stderr, "output: " + str(args.outputfile.name)

    with etl_util.error_reporting():
        make_snow(args.inputfile, args.outputfile, args.no_comments)
        args.inputfile.close()
        args.outputfile.close()
        print >> sys.stderr, "done translating " + args.inputfile.name

@rayabhijit21, I am fine with you doing whatever you want with the code I wrote that is posted by Snowflake at https://community.snowflake.com/s/scripts. I no longer work for Snowflake, so if you are looking for official permission from Snowflake, I suggest you reach out to them directly.

@hersker13 ok. Thank you for your clarification. I've dropped an email to [email protected] regarding the same.

To call the sccript in terminal you. can use it like this
python ddl_conversion.py <Redshift-SQL.sql> <Snow-SQL.sql> # replace with your sql input and sql output file names.

Also @tamiroze , I used the latest file as you suggested above, it it seems to have an issue when converts create CREATE TABLE IF NOT EXISTS statement to snowflake. It converts it into this: CREATE OR REPLACE TABLE IF NOT EXISTS
I guess the logic is somewhere on line 145 # CREATE TABLE => CREATE OR REPLACE TABLE

Hi again @tamiroze , I've noticed that this script does not cover a case to translate GETDATE() in PostgreSQL into CAST(CURRENT_TIMESTAMP() AS DATE)
SQL compilation error: Default value data type does not match data type for column _RECORD_CREATED_ON
the column definition in PostgreSQL (Redshift) is
record_created_on DATE DEFAULT getdate()