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Paul Delannoy f7e8aaa2d8 'Oracle-to-PostgreSQL Migration Expert' Custom Agent: Update Custom Agent & Plugin & Skills (#2566 )

* Enhance Oracle-to-PostgreSQL migration skills and documentation

- Update migration agent guidelines to prioritize extension tool usage for code migration.
- Refine migration phases with detailed steps for pre-migration review and schema migration.
- Add new reviewing skill references for PostgreSQL materialized view refresh and UNION ALL planner risks.
- Ensure consistency in collation handling and testing strategies across skills.

* - Review migration phases to ensure correct order of execution
- Add exit criteria to each migration phase
- Remove invocation of `ms-ossdata.vscode-pgsql` extension due to dependency on VSCode
- Update README.md to reflect changes in migration phases and exit criteria
- Update broken reference to custom agent in plugin.json

* Enhance downstream migration skills and following custom agent improvements

- Added new skill for migrating .NET data access code from Oracle to PostgreSQL.
- Updated README to include new migration skill.
- Improved existing skills with clearer file naming conventions and migration actions.
- Added reference documents for handling Oracle-specific functions and pagination.
- Created detailed guides for NVL, DECODE, ROWNUM, SYSDATE, and DUAL replacements.

* Clarify PostgreSQL schema immutability and stored procedure migration risks

* Update target schema path in migration documentation for clarity

* fix(skills): clarify Phase 3-only scope for Oracle test skills

Both Oracle test skills were ambiguously worded in ways that could
cause a model to invoke them during Phase 6 (PostgreSQL test migration)
instead of using them exclusively in Phase 3.

Key changes:
- Rewrite descriptions to explicitly state Phase 3-only usage and
  warn against invoking during Phase 6
- Replace "scaffold for Oracle first" with "Oracle only" to remove
  the false implication of a second PostgreSQL scaffolding step
- Replace "Tests validate behavior consistency when running against
  Oracle or PostgreSQL" with clear Oracle-only framing
- Rename "DB-agnostic assertions" → "Assertion portability" and
  explain the why (survive Phase 6 migration without rewrites)
- Fix datetime bullet in integration tests skill to use generic
  Oracle column precision language instead of PostgreSQL type syntax
- Name Oracle NuGet package explicitly (Oracle.ManagedDataAccess.Core)

* feat(oracle-to-postgres): gate Phase 1 on DDL presence; add DDL scan to Phase 2 risk analysis

- Phase 1 success criteria now requires Oracle DDL artifacts to be
  confirmed present at the recorded location before proceeding.
  If missing, the agent stops and prompts the user to provide them.

- Phase 2 risk analysis now explicitly scans DDL/Oracle/{ProjectName}/
  as supplemental context, summarising procedure complexity indicators
  (dynamic SQL, DBMS_* / UTL_* references, autonomous transactions,
  pipelined functions, BULK COLLECT/FORALL, REF CURSOR, TYPE bodies)
  rather than ingesting DDL files wholesale. This ensures schema-level
  migration risk is captured even when it isn't visible in application
  code alone.

* - Merge in latest 'main' changes
- Update custom agent plugin (eg resolve conflict and add new skill)
- Validate skills
- Run build

* chore(plugin.json): update version to 1.1.0

* feat(oracle-to-postgres): update version to 1.1.0 for migration expert plugin

* fix: add INOUT to ignore-words-list for PostgreSQL migration

---------

Co-authored-by: TCPrimedPaul <paul.delannoy@tc.gc.ca>

2026-08-11 12:47:51 +10:00

2.4 KiB

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Oracle to PostgreSQL: NVL, DECODE, and Null-Handling Functions

Problem

Oracle provides several functions — NVL, NVL2, DECODE — that have no direct equivalents in standard SQL but are commonly used in Oracle stored procedures and inline SQL. PostgreSQL uses standard SQL alternatives: COALESCE, NULLIF, and CASE expressions.

Behavior Comparison

NVL

Oracle: NVL(expr, replacement) — returns replacement if expr is NULL, otherwise expr.

PostgreSQL: Use COALESCE(expr, replacement) — semantically identical for two arguments.

-- Oracle
NVL(column_name, 'default')

-- PostgreSQL
COALESCE(column_name, 'default')

NVL2

Oracle: NVL2(expr, not_null_val, null_val) — returns not_null_val if expr IS NOT NULL, null_val if NULL.

PostgreSQL: No direct equivalent — use CASE:

-- Oracle
NVL2(column_name, 'has value', 'no value')

-- PostgreSQL
CASE WHEN column_name IS NOT NULL THEN 'has value' ELSE 'no value' END

DECODE

Oracle: DECODE(expr, search1, result1, search2, result2, ..., default) — equality-based switch.

PostgreSQL: No DECODE function — use CASE WHEN:

-- Oracle
DECODE(status, 1, 'Active', 2, 'Inactive', 'Unknown')

-- PostgreSQL
CASE status
  WHEN 1 THEN 'Active'
  WHEN 2 THEN 'Inactive'
  ELSE 'Unknown'
END

Note: DECODE in Oracle treats two NULL values as equal (unlike =). If any search value is NULL, use IS NULL in the CASE equivalent:

-- Oracle: DECODE treats NULL = NULL
DECODE(col, NULL, 'empty', col)

-- PostgreSQL
CASE WHEN col IS NULL THEN 'empty' ELSE col END

Migration Actions

1. Stored Procedures

Apply the direct substitutions above. Pay special attention to:

NVL on numeric expressions — COALESCE is type-sensitive in PostgreSQL; ensure both arguments are the same type or cast explicitly.
DECODE with NULL search values — replace with IS NULL guard in the CASE expression.

2. Application Code (inline SQL strings)

Search C# string literals and query builders for NVL(, NVL2(, and DECODE(. Apply the same substitutions.

3. Tests

Write test cases that exercise NULL inputs specifically — the Oracle → PostgreSQL translation of NVL/COALESCE is straightforward, but edge cases around NULL equality in DECODE → CASE are a common source of silent behavioral differences.

2.4 KiB Raw Blame History