Update README.md

README.md

@@ -29,7 +29,7 @@ pretty_name: osti
 | **Conference Papers** | 246,227 |
 | **With Full-Text Available** | 558,050 (100%) |
 | **Date Range** | 1943 – Present |
-| **Metadata Size** | ~228 MB (Parquet) |
+| **Metadata Size** | ~348 MB (Parquet) |
 | **Estimated PDF Corpus** | ~80–150 GB |
 | **Source** | [OSTI.GOV API v1](https://www.osti.gov/api/v1/docs) |
 
@@ -44,7 +44,7 @@ This dataset was harvested using the **Lazy Pointer** architecture: metadata and
 │  YOUR MACHINE (30GB RAM, 20GB Disk)                         │
 │  ┌──────────────────┐    ┌──────────────────┐              │
 │  │  Metadata Harvest │───▶│  SQLite / Parquet │              │
-│  │  (REST API)       │    │  (228 MB)         │              │
+│  │  (REST API)       │    │  (348 MB)         │              │
 │  └──────────────────┘    └──────────────────┘              │
 │           │                                                │
 │           ▼                                                │
@@ -77,8 +77,8 @@ This dataset was harvested using the **Lazy Pointer** architecture: metadata and
 
 | File | Description | Size |
 |------|-------------|------|
-| `osti_metadata.parquet` | Core dataset with all metadata + lazy pointers | ~228 MB |
-| `osti_metadata.sqlite` | SQLite source (optional, for local querying) | ~350 MB |
+| `osti_metadata.parquet` | Core dataset with all metadata + lazy pointers | ~348 MB |
+| `osti_metadata.sqlite` | SQLite source (optional, for local querying) | ~1 GB |
 
 ---
 
@@ -95,7 +95,8 @@ This dataset was harvested using the **Lazy Pointer** architecture: metadata and
     "publication_date": "2002-09-01",           # ISO-8601 date
     "subjects": '["energy", "building"]',       # JSON list of keywords
     "fulltext_url": "https://www.osti.gov/servlets/purl/944980",  # PDF URL
-    "pdf_downloaded": 0                          # 0 = not yet fetched, 1 = fetched
+    "pdf_downloaded": 0,                         # 0 = not yet fetched, 1 = fetched
+    "harvested_at": "20260719_163215"           # Harvest batch timestamp
 }
 ```
 
@@ -117,7 +118,7 @@ This dataset was harvested using the **Lazy Pointer** architecture: metadata and
 ```python
 import pandas as pd
 
-df = pd.read_parquet("osti_metadata.parquet")
+df = pd.read_parquet("osti/osti_metadata.parquet")
 print(f"Total records: {len(df)}")
 
 # Filter by subject
@@ -200,7 +201,7 @@ contract = df[df['abstract'].str.contains('DE-AC02', case=False, na=False)]
 1. **Reconnaissance** — Queried OSTI API to count records per `product_type` with `has_fulltext=true`
 2. **Metadata Harvest** — Streamed 558K records via REST API (500 records/page), parsed with `ijson`, stored in SQLite
 3. **Checkpointing** — Saved `last_page` after every API request to survive crashes
-4. **Compression** — Converted SQLite to Parquet with Zstd compression (~35% smaller)
+4. **Compression** — Converted SQLite to Parquet with PyArrow row-group chunking to optimize memory
 5. **Upload** — Pushed Parquet to Hugging Face, freed local disk
 
 ### Rate Limiting
@@ -279,4 +280,4 @@ This is a living dataset. To contribute:
 
 ---
 
-*Built with 16GB RAM, 1TB disk, 12 v-cores, and 8TB of Hugging Face storage. No scraping — just polite API harvesting.* 🚀
+*Built with 16GB RAM, 1TB disk, 12 v-cores, and 8TB of Hugging Face storage. No scraping — just polite API harvesting.* 🚀