Data Migration

Phase 2: Inspect Target

• Check if target schema/database exists using list_tables(database=target)
• If target table already exists, use describe_table(database=target) to compare
• Determine whether to create new or replace existing

Phase 3: Build Target DDL

• Map source column types to target dialect (DuckDB types to Greenplum/StarRocks types)
• For StarRocks: determine DUPLICATE KEY columns and DISTRIBUTED BY HASH strategy
• Generate CREATE TABLE DDL appropriate for target database
• Execute DDL with execute_ddl(sql, database=target)

Phase 4: Transfer Data

• Use transfer_query_result(source_sql, source_database, target_table, target_database, mode) to move data
• For fresh migration use mode='replace' (truncates target first)
• For incremental load use mode='append'
• Verify the transfer result (rows_transferred count)

Phase 5: Reconcile

Run all reconciliation checks using read_query(database=...) on both source and target. Checks must be executed in this order:

1. Row count - Total row count comparison
2. Null ratio - Null count per column comparison
3. Min/max - Range comparison for numeric and date columns
4. Distinct count - Cardinality comparison for key columns
5. Duplicate key - Check for duplicate keys in target
6. Sample diff - Key-based row sample comparison (top 10)
7. Numeric aggregate - SUM/AVG comparison for numeric columns

Phase 6: Report

Summarize migration results including:

• Source and target table names
• Rows transferred
• Each reconciliation check with pass/fail status
• Any issues or warnings

Critical rules

• Always specify the database parameter explicitly in every tool call
• Source database is read-only: never execute DDL or write operations against it
• Target database is write-target: all DDL and writes go here
• Reconciliation is mandatory: never skip it after data transfer
• Report all reconciliation results even if some checks fail
• NEVER fall back to a different database if the target is unavailable — STOP and report the error
• Before starting, verify both source and target show "available": true in list_databases() output

Checklist

• Migration checklist: references/checklist.md

Output expectations

At minimum, return:

• source and target database/table names
• rows transferred
• reconciliation check results with pass/fail
• blocking issues that must be addressed