Created
November 17, 2017 09:14
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Add a primary key to a sqlite table
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import re | |
def get_create_table_string(tablename, connection): | |
sql = """ | |
select * from sqlite_master where name = "{}" and type = "table" | |
""".format(tablename) | |
result = connection.execute(sql) | |
create_table_string = result.fetchmany()[0][4] | |
return create_table_string | |
def add_pk_to_create_table_string(create_table_string, colname): | |
regex = "(\n.+{}[^,]+)(,)".format(colname) | |
return re.sub(regex, "\\1 PRIMARY KEY,", create_table_string) | |
def add_pk_to_sqlite_table(tablename, index_column, connection): | |
cts = get_create_table_string(tablename, connection) | |
cts = add_pk_to_create_table_string(cts, index_column) | |
template = """ | |
BEGIN TRANSACTION; | |
ALTER TABLE {tablename} RENAME TO {tablename}_old_; | |
{cts}; | |
INSERT INTO {tablename} SELECT * FROM {tablename}_old_; | |
DROP TABLE {tablename}_old_; | |
COMMIT TRANSACTION; | |
""" | |
create_and_drop_sql = template.format(tablename = tablename, cts = cts) | |
connection.executescript(create_and_drop_sql) | |
# Example: | |
# import pandas as pd | |
# import sqlite3 | |
# df = pd.DataFrame({"a": [1,2,3], "b": [2,3,4]}) | |
# con = sqlite3.connect("deleteme.db") | |
# df.to_sql("df", con, if_exists="replace") | |
# add_pk_to_sqlite_table("df", "index", con) | |
# r = con.execute("select sql from sqlite_master where name = 'df' and type = 'table'") | |
# print(r.fetchone()[0]) |
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Hi, is it possible to tweak this to nominate a column to become the PK, as opposed to creating a new, sequential one?