SAV File Size Increases Significantly After Metadata Update and adding Column

[Sushants2789]

Description

When using pyreadstat to read a SAV file, add columns, and save back, the output file size increases substantially without a proportional increase in actual data content.

Detailed Reproduction Steps

Read SAV file with encoding detection
`import pyreadstat
import chardet

Encoding detection

with open(file_path, 'rb') as file:
raw_data = file.read(10000)
result = chardet.detect(raw_data)
detected_encoding = result['encoding'] or 'utf-8'

Read file

sav_df, meta = pyreadstat.read_sav(file_path, encoding=detected_encoding)

Add new columns

new_column_labels = meta.column_labels.copy()
new_value_labels = meta.variable_value_labels.copy()

Write file back

temp_sav_path = sav_file_path.replace('.sav', '_updated.sav')
pyreadstat.write_sav(
sav_df,
temp_sav_path,
column_labels=new_column_labels,
variable_value_labels=new_value_labels
)

Environment Details

pyreadstat version: 1.2.8
Platform: macOS
Python version: 3.9.18