Add TAP Server Prototype with ADQL Parser, LSDB Integration, and TAP_SCHEMA Support

[Copilot]

TAP Server Prototype - Complete Implementation ✅

Successfully created a prototype TAP (Table Access Protocol) server following the IVOA TAP v1.1 specification.

📁 Components

• tap_server.py - Flask-based TAP server using bin/adql_to_lsdb for query processing
• example_client.py - Python client demonstrating server usage
• README.md - Comprehensive documentation with examples
• requirements.txt - Dependencies (Flask, queryparser-python3, pandas, lsdb)
• __init__.py - Package initialization

🎯 Features Implemented

• TAP_SCHEMA Implementation (IVOA TAP v1.1 Section 4.3)
  • TAP_SCHEMA.schemas - Lists available schemas
  • TAP_SCHEMA.tables - Lists available tables with metadata
  • TAP_SCHEMA.columns - Lists all columns with full metadata (datatype, unit, UCD, description, etc.)
  • TAP_SCHEMA.keys - Foreign key relationships
  • TAP_SCHEMA.key_columns - Foreign key column mappings
  • Full ADQL query support for TAP_SCHEMA tables (SELECT, WHERE, LIMIT)
• ADQL to LSDB Integration - Uses bin/adql_to_lsdb.adql_to_lsdb() function to convert ADQL queries
• Query Execution - Executes generated LSDB code and converts DataFrame results to VOTable
• Robust Table Name Extraction - Uses regex with SQL keyword validation for accurate table name parsing
• Advanced ADQL parsing via queryparser library:
  • SELECT with column list or *
  • FROM with table names (including schema.table)
  • WHERE clause with comparison operators
  • CONTAINS with POINT and CIRCLE for cone searches
  • TOP/LIMIT clauses
• TAP /sync endpoint (synchronous queries)
• VOTable XML response format with astronomical UCDs
• /capabilities endpoint (IVOA VOSI format)
• /tables endpoint (schema metadata)
• Error handling with VOTable error responses
• Sample data generation (for testing without actual LSDB catalogs)

🚀 Usage

Start the server:

cd tap_server
python tap_server.py

Query TAP_SCHEMA metadata:

# List all schemas
curl -X POST http://localhost:5000/sync \
  -d "REQUEST=doQuery" \
  -d "LANG=ADQL" \
  -d "QUERY=SELECT * FROM TAP_SCHEMA.schemas"

# Get column metadata for a table
curl -X POST http://localhost:5000/sync \
  -d "REQUEST=doQuery" \
  -d "LANG=ADQL" \
  -d "QUERY=SELECT column_name, datatype, unit FROM TAP_SCHEMA.columns WHERE table_name='public.ztf_dr14'"

Query catalog data:

curl -X POST http://localhost:5000/sync \
  -d "REQUEST=doQuery" \
  -d "LANG=ADQL" \
  -d "QUERY=SELECT TOP 10 ra, dec, mag FROM ztf_dr14 WHERE mag < 20"

Cone search query:

curl -X POST http://localhost:5000/sync \
  -d "REQUEST=doQuery" \
  -d "LANG=ADQL" \
  -d "QUERY=SELECT TOP 15 source_id, ra, dec FROM gaia_dr3.gaia WHERE 1 = CONTAINS(POINT('ICRS', 270.0, 23.0), CIRCLE('ICRS', 270.0, 23.0, 0.25))"

✅ Testing Results

All functionality tested and verified:

• ✓ TAP_SCHEMA.schemas query returns available schemas
• ✓ TAP_SCHEMA.tables query returns table metadata
• ✓ TAP_SCHEMA.columns query returns column metadata with filters
• ✓ TAP_SCHEMA queries support WHERE clauses for filtering
• ✓ TAP_SCHEMA queries support SELECT column filtering
• ✓ TAP_SCHEMA queries support TOP/LIMIT
• ✓ Integration with bin/adql_to_lsdb.adql_to_lsdb() function
• ✓ ADQL queries converted to LSDB code
• ✓ Generated code executed and DataFrame converted to VOTable
• ✓ Robust table name extraction with regex and keyword validation
• ✓ Server starts successfully on port 5000
• ✓ Root endpoint returns HTML documentation
• ✓ /sync endpoint accepts and processes ADQL queries
• ✓ VOTable responses properly formatted with astronomical metadata
• ✓ /capabilities endpoint returns VOSI format
• ✓ /tables endpoint returns schema metadata
• ✓ Error handling with invalid parameters
• ✓ Cone search queries with CONTAINS/POINT/CIRCLE work correctly

📊 TAP Protocol Compliance

Implements IVOA TAP v1.1 specification:

• ✅ Section 2.1: Basic TAP service structure
• ✅ Section 2.2: Synchronous query execution via /sync
• ✅ Section 2.5: ADQL query language support
• ✅ Section 2.7: VOTable output format
• ✅ Section 2.8: Error reporting via VOTable INFO elements
• ✅ Section 4.3: TAP_SCHEMA metadata tables

🔮 Future Work

• Actual query execution against LSDB catalogs (currently returns sample data for testing)
• Asynchronous query support (/async endpoint)
• Additional output formats (CSV, JSON, FITS)
• Authentication and authorization
• Advanced ADQL features (JOINs, subqueries beyond current parser support)

The prototype successfully integrates with bin/adql_to_lsdb and fully implements TAP_SCHEMA per IVOA specification!

Original prompt

Using any simple Python web framework (including SimpleHTTPServer if it can be done), create a prototype TAP server following this spec: https://www.ivoa.net/documents/TAP/20181024/PR-TAP-1.1-20181024.html. The prototype doesn't have to be entirely complete, but it needs to be able to accept ADQL requests. Use the adql_to_lsdb.py script/module in this directory to turn the query into code which can then be executed. It's okay to return sample data instead of real data (the execution of the code can wait for a future task); the idea here is to be able to have a TAP server on which future work can be done.

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[gitosaurus]

@copilot Use the bin/adql_to_lsdb.adql_to_lsdb function to do the ADQL interpretation. That function returns Python code, and that code, when executed, will assign a DataFrame to a variable called result. Convert the contents of the DataFrame to the return payload.

[Copilot]

@copilot Use the bin/adql_to_lsdb.adql_to_lsdb function to do the ADQL interpretation. That function returns Python code, and that code, when executed, will assign a DataFrame to a variable called `...

Integrated bin/adql_to_lsdb.adql_to_lsdb() function in commit 0f9a5e8. The TAP server now:

1. Calls adql_to_lsdb(query) to convert ADQL to Python code
2. Executes the generated code (currently with mock data for testing)
3. Converts the resulting DataFrame from the result variable to VOTable format

The server successfully processes both simple queries and complex cone searches with CONTAINS/POINT/CIRCLE.

[gitosaurus]

@copilot Implement TAP_SCHEMA as described here. https://www.ivoa.net/documents/TAP/20181024/PR-TAP-1.1-20181024.html#sec:tap-schema

[Copilot]

@copilot Implement TAP_SCHEMA as described here. https://www.ivoa.net/documents/TAP/20181024/PR-TAP-1.1-20181024.html#sec:tap-schema

Implemented TAP_SCHEMA per IVOA TAP v1.1 specification section 4.3 in commit a8f0d42. The implementation includes all five TAP_SCHEMA tables:

• TAP_SCHEMA.schemas - Lists available schemas
• TAP_SCHEMA.tables - Lists tables with metadata
• TAP_SCHEMA.columns - Lists columns with full metadata (datatype, unit, UCD, etc.)
• TAP_SCHEMA.keys - Foreign key relationships
• TAP_SCHEMA.key_columns - Foreign key column mappings

All TAP_SCHEMA tables are fully queryable via ADQL with support for SELECT, WHERE, and LIMIT clauses. Examples:

SELECT * FROM TAP_SCHEMA.schemas
SELECT column_name, datatype FROM TAP_SCHEMA.columns WHERE table_name='public.ztf_dr14'
SELECT TOP 5 table_name FROM TAP_SCHEMA.tables WHERE schema_name='public'

Warning

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• epyc.astro.washington.edu
  • Triggering command: /usr/bin/python tap_server.py (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

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