Optimizing LLM Queries for CSV Files to Minimize Token Usage: A Beginner's Guide

When working with large CSV files and querying them using a Language Model (LLM), optimizing your approach to minimize token usage is crucial. This helps reduce costs, improve performance, and make your system more efficient. Here’s a beginner-friendly guide to help you understand how to achieve this.

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What Are Tokens, and Why Do They Matter?

Tokens are the building blocks of text that LLMs process. A single word like "cat" or punctuation like "." counts as a token. Longer texts mean more tokens, which can lead to higher costs and slower query responses. By optimizing how you query CSV data, you can significantly reduce token usage.

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Key Strategies to Optimize LLM Queries for CSV Files

1. Preprocess and Filter Data

Before sending data to the LLM, filter and preprocess it to retrieve only the relevant rows and columns. This minimizes the size of the input text.

How to Do It:

• Use Python or database tools to preprocess the CSV file.
• Filter for only the rows and columns necessary for your query.

  import pandas as pd
  
  # Load CSV file
  df = pd.read_csv("data.csv")
  
  # Filter relevant data
  filtered_df = df[df["Category"] == "AI"]
  filtered_df = filtered_df[["Name", "Score"]]
  
  # Save filtered data to a smaller CSV file
  filtered_df.to_csv("filtered_data.csv", index=False)
  

Benefit: Instead of sending an entire CSV file, you send only the required subset of data.

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2. Summarize Data

Use aggregation or summarization techniques to condense the data before passing it to the LLM.

Example Use Case:
Instead of sending 1,000 rows of sales data, aggregate it at a higher level:

• Compute totals, averages, or other metrics.
• Pass only the summary (e.g., "Total sales for 2025: $1,000,000").

summary = df.groupby("Year")["Sales"].sum()
summary_text = f"Total sales by year: {summary.to_dict()}"

Benefit: A single line of summary text replaces thousands of rows, saving tokens.

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3. Use Metadata for Efficient Queries

Add metadata to your CSV file, such as tags or categories, to make filtering easier and faster.

Example:
If your CSV contains transaction logs, include metadata like:

• Date
• Category
• Priority

Instead of passing raw logs, query the metadata first:

• Query: "Show me high-priority transactions from June 2025."
• Result: Filtered data with only relevant rows.

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4. Chunk Large Data

If your CSV file is too large to process at once, split it into smaller chunks and query the LLM sequentially.

How to Do It:

• Divide the file into multiple parts.
• Process each chunk individually.
• Combine the results.

# Split CSV into chunks
chunk_size = 100  # Number of rows per chunk
for i, chunk in enumerate(pd.read_csv("large_file.csv", chunksize=chunk_size)):
    chunk.to_csv(f"chunk_{i}.csv", index=False)

Benefit: Smaller chunks fit within the LLM’s context window, reducing token usage.

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5. Use Embedding-Based Search

Convert your CSV data into embeddings (vector representations). Store these embeddings in a vector database and perform similarity searches to retrieve the most relevant rows for your query.

Tools to Use:

• Use libraries like sentence-transformers to generate embeddings.
• Store them in vector databases like Pinecone or Weaviate.

Example:

• Query: "Find rows similar to 'AI projects with a score above 90'."
• Result: Only the top 5–10 most relevant rows are sent to the LLM.

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6. Pre-Format Data

Format your data into a compact structure, like JSON or a short table, before sending it to the LLM.

Example:
Instead of sending raw CSV rows:

Name, Score, Category
Alice, 95, AI
Bob, 88, Data Science

Send this:

[{"Name": "Alice", "Score": 95, "Category": "AI"}]

Benefit: Structured data reduces unnecessary tokens and improves query clarity.

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7. Leverage Caching

Cache the results of frequently used queries. If a query has already been processed, return the cached result instead of re-querying the LLM.

How to Implement:

• Use a key-value store (e.g., Redis) to save query results.
• Check the cache before querying the LLM.

Example:

• Query: "Summarize sales data for 2025."
• Cache lookup: Return the previously computed summary if available.

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8. Ask Specific Questions

Frame your queries to be as specific as possible. Avoid open-ended or vague queries, as they may require processing more data.

Example:

• Instead of: "Tell me about the CSV file."
• Ask: "What are the top 5 products by sales in 2025?"

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A Practical Workflow for CSV Optimization

1. Load and Preprocess Data

   • Use Python or database tools to filter and preprocess the CSV.

2. Summarize or Chunk Data

   • Aggregate or split the data into smaller sets.

3. Query Efficiently

   • Use metadata or embeddings to retrieve only relevant rows.

4. Send Compact Data to LLM

   • Format the filtered data into a compact structure.

5. Cache Results

   • Store frequently queried results to avoid redundant token usage.

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Example Query Optimization

Scenario: You have a CSV file with 1,000 rows of sales data. You want to know the top 3 products by sales.

Non-Optimized Query:

"Here is my CSV file: [entire 1,000 rows]. What are the top 3 products by sales?"

Optimized Query:

1. Preprocess the CSV:

   top_products = df.groupby("Product")["Sales"].sum().nlargest(3)
   

2. Send the result to the LLM:

   "These are the top 3 products by sales: {'Product A': 500, 'Product B': 450, 'Product C': 400}. Provide insights on these."
   

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Conclusion

By filtering, summarizing, and structuring your data before querying an LLM, you can significantly reduce token usage and costs. Start small, experiment with these techniques, and gradually build an efficient workflow for handling large CSV files. Happy optimizing! 🚀