Merge pull request #1 from cid-harvard/Readme

Update README.md

Author: bleonard33

README.md

@@ -1 +1,31 @@
-# pandas-to-postgres
+# Pandas-to-postgres
+
+Pandas-to-postgres allows you to bulk load the contents of large dataframes into postgres as quickly as possible. The main differences from pandas' `to_sql` functions are:
+
+- Uses `COPY` combined with `to_csv` instead of `execute / executemany`, which runs much faster for large volumes of data
+- Uses `COPY FROM STDIN` with `StringIO` to avoid IO overhead to intermediate files. This matters in particular for data stored in unusual formats like HDF, STATA, parquet - common in the scientific world.
+- Chunked loading methods to be able to load larger-than-memory tables. In particular the HDF5 functions load data in chunks directly from the file, easily extendible to other formats that support random access by row range.
+- Removes indexing overhead by automatically detecting and dropping indexes before load, and then re-creating them afterwards
+- Loads separate tables in parallel using multiprocessing
+- Hooks to modify data as it's loaded 
+
+# Dependencies 
+
+- Python 3
+- psycopg2 (for the low level COPY from stdin)
+- sqlalchemy (for reflection for indexes)
+- pandas
+
+# Usage Example
+
+```python3
+
+from pandas_to_postgres import ...
+
+# already loaded dataframe
+...
+
+# HDF from file
+...
+
+```