How to insert several thousand columns into sqlite3?

Question

Similar to my last question, but I ran into problem lets say I have a simple dictionary like below but its Big, when I try inserting a big dictionary using the methods below I get operational error for the c.execute(schema) for too many columns so what should be my alternate method to populate an sql databases columns? Using the alter table command and add each one individually?

import sqlite3
con = sqlite3.connect('simple.db')
c = con.cursor()

dic = {
    'x1':{'y1':1.0,'y2':0.0},
    'x2':{'y1':0.0,'y2':2.0,'joe bla':1.5},
    'x3':{'y2':2.0,'y3 45 etc':1.5}
    }

# 1. Find the unique column names.
columns = set()
for _, cols in dic.items():
    for key, _ in cols.items():
       columns.add(key)

# 2. Create the schema.
col_defs = [
    # Start with the column for our key name
    '"row_name" VARCHAR(2) NOT NULL PRIMARY KEY'
    ]
for column in columns:
    col_defs.append('"%s" REAL NULL' % column)
schema = "CREATE TABLE simple (%s);" % ",".join(col_defs)
c.execute(schema)

# 3. Loop through each row
for row_name, cols in dic.items():

    # Compile the data we have for this row.
    col_names = cols.keys()
    col_values = [str(val) for val in cols.values()]

    # Insert it.
    sql = 'INSERT INTO simple ("row_name", "%s") VALUES ("%s", "%s");' % (
        '","'.join(col_names),
        row_name,
        '","'.join(col_values)
        )

Answer 1

If I understand you right, you're not trying to insert thousands of rows, but thousands of columns. SQLite has a limit on the number of columns per table (by default 2000), though this can be adjusted if you recompile SQLite. Never having done this, I do not know if you then need to tweak the Python interface, but I'd suspect not.

You probably want to rethink your design. Any non-data warehouse / OLAP application is highly unlikely to need or be terribly efficient with thousands of columns (rows, yes) and SQLite is not a good solution for a data warehouse / OLAP type situation. You may get a bit further with something like an entity-attribute-value setup (not a normal recommendation for genuine relational databases, but a valid application data model and much more likely to accommodate your needs without pushing the limits of SQLite too far).