-- =====================================================
-- MIGRATION: Add composite indexes to ml.predictions for performance
-- =====================================================
-- Date: 2026-02-03
-- Task: ST-3.4, GAP-008
-- Description: Optimize query performance with composite indexes
-- =====================================================

-- ===========================================
-- COMPOSITE INDEX 1: Symbol + Timeframe + Created
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE symbol = ? AND timeframe = ?
--                ORDER BY created_at DESC LIMIT ?
-- Use case: Most common query for fetching latest predictions for a symbol/timeframe
CREATE INDEX IF NOT EXISTS idx_predictions_symbol_timeframe_created
ON ml.predictions(symbol, timeframe, created_at DESC);

-- ===========================================
-- COMPOSITE INDEX 2: Symbol + Prediction Type + Created
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE symbol = ? AND prediction_type = ?
--                ORDER BY created_at DESC
-- Use case: Filtered queries by prediction type (e.g., only DIRECTION predictions)
CREATE INDEX IF NOT EXISTS idx_predictions_symbol_type_created
ON ml.predictions(symbol, prediction_type, created_at DESC);

-- ===========================================
-- COMPOSITE INDEX 3: Model + Symbol + Timeframe + Created
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE model_id = ? AND symbol = ? AND timeframe = ?
--                ORDER BY created_at DESC
-- Use case: Model-specific prediction queries for analysis and comparison
CREATE INDEX IF NOT EXISTS idx_predictions_model_symbol_timeframe
ON ml.predictions(model_id, symbol, timeframe, created_at DESC);

-- ===========================================
-- COMPOSITE INDEX 4: High Confidence Predictions (Partial)
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE symbol = ? AND timeframe = ? AND confidence_score >= 0.7
--                ORDER BY created_at DESC
-- Use case: Fetch only high-confidence predictions for display/alerts
CREATE INDEX IF NOT EXISTS idx_predictions_high_confidence
ON ml.predictions(symbol, timeframe, created_at DESC)
WHERE confidence_score >= 0.7;

-- ===========================================
-- COMPOSITE INDEX 5: Recent Valid Predictions (Partial)
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE symbol = ? AND timeframe = ? AND valid_until > NOW()
--                ORDER BY prediction_type, created_at DESC
-- Use case: Active predictions that haven't expired yet
-- Note: Uses immutable predicate-safe pattern (valid_until compared at query time)
CREATE INDEX IF NOT EXISTS idx_predictions_recent_valid
ON ml.predictions(symbol, timeframe, prediction_type, created_at DESC)
WHERE valid_until IS NOT NULL;

-- ===========================================
-- COMPOSITE INDEX 6: Overlay Display for Charts
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE symbol = ? AND timeframe = ?
--                  AND (chart_config->>'show_on_chart')::boolean = true
--                ORDER BY display_priority DESC, created_at DESC
-- Use case: Chart rendering - fetch predictions configured for display
CREATE INDEX IF NOT EXISTS idx_predictions_overlay_display
ON ml.predictions(symbol, timeframe, display_priority DESC, created_at DESC)
WHERE (chart_config->>'show_on_chart')::boolean = true;

-- ===========================================
-- COMPOSITE INDEX 7: Symbol + Confidence Score (Descending)
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE symbol = ?
--                ORDER BY confidence_score DESC
-- Use case: Ranking predictions by confidence for a symbol
CREATE INDEX IF NOT EXISTS idx_predictions_symbol_confidence
ON ml.predictions(symbol, confidence_score DESC, created_at DESC);

-- ===========================================
-- COMPOSITE INDEX 8: Timeframe + Prediction Result + Created
-- ===========================================
-- Query pattern: SELECT * FROM ml.predictions
--                WHERE timeframe = ? AND prediction_result = ?
--                ORDER BY created_at DESC
-- Use case: Cross-symbol analysis of specific prediction results (e.g., all BUY signals on 1H)
CREATE INDEX IF NOT EXISTS idx_predictions_timeframe_result_created
ON ml.predictions(timeframe, prediction_result, created_at DESC)
WHERE prediction_result IS NOT NULL;

-- ===========================================
-- DOCUMENTATION NOTES
-- ===========================================
-- Performance considerations:
-- 1. These indexes are designed for read-heavy workloads
-- 2. Partial indexes reduce storage and improve write performance
-- 3. DESC ordering on timestamps optimizes LIMIT queries for recent data
-- 4. Run ANALYZE after creation in production:
--    ANALYZE ml.predictions;
--
-- Index maintenance:
-- - Monitor pg_stat_user_indexes for usage statistics
-- - Consider REINDEX CONCURRENTLY if fragmentation occurs
-- - Review query plans with EXPLAIN ANALYZE periodically