Matrix Builder: Add cost estimation and smart row-count prediction

[sfc-gh-obielov]

Triage note (2026-04-23): Part of the Matrix Builder epic alongside #35 (road-aware tessellation). Land #35 first. Without #35's road-aware filter toggle, this ticket's estimator would systematically over-predict hex counts (and therefore rows, credits, and duration) for any region with significant uninhabited area. The ESTIMATE_MATRIX_COST procedure must accept the road_filter flag as an input and return distinct estimates for filter ON vs OFF; calibrate both against historical runs.

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Summary

Add a pre-flight cost estimation feature to the Matrix Builder that, given a user's configuration (region, resolution, routing profile, bounding box, etc.), predicts:

1. Resulting matrix row count — smart calculation based on tessellation resolution and region geometry, before any compute runs.
2. Expected Snowflake query cost — warehouse credits consumed for the SQL-side work (tessellation, matrix assembly, writes).
3. Expected SPCS / ORS compute cost — compute-pool credits consumed by ORS services answering matrix calls.
4. Expected wall-clock duration — based on historical runs of comparable shapes/resolutions.

The goal is to let users make an informed choice before kicking off a potentially expensive matrix build.

Motivation

Today users configure a region + H3 resolution + routing profile and click build with no visibility into:

• How many origin/destination pairs this will produce (can easily be millions)
• How many warehouse credits will be burned
• How much SPCS compute the ORS services will consume
• How long it will take

This leads to surprise bills, stuck long-running jobs, and unrealistic resolutions (e.g. res 9 over a metropolitan region).

Proposed Work

1. Smart row-count estimation

• Compute the effective tessellation cell count for the chosen region + resolution without materializing the tessellation.
  • Use ST_AREA(region_geometry) divided by average H3 cell area at the chosen resolution, adjusted for coastline/boundary clipping.
  • Validate against actual counts from previously-built regions; store calibration factors per resolution.
• Resulting matrix rows = cells * cells (or cells * cells - cells if diagonal excluded).
• Surface both the cell count and the matrix row count in the UI before the user confirms.

2. Query cost estimation

• Reuse historical QUERY_HISTORY credits-used data for prior matrix builds, keyed by (region_size_bucket, h3_resolution, profile).
• Formula: estimated_credits = base_cost + per_cell_cost * cell_count + per_pair_cost * pair_count.
• Fit coefficients from QUERY_HISTORY / SERVERLESS_TASK_HISTORY for matrix pipeline queries (filter by query_tag origin sf_sit-is-fleet).

3. SPCS / ORS compute cost estimation

• ORS matrix calls scale roughly with pair_count and routing profile complexity (driving-car < cycling < foot-walking < hgv).
• Derive per-profile throughput (pairs/sec) and compute-pool credit rate from historical SPCS runs.
• Surface a separate "ORS compute" line item alongside warehouse credits.

4. UI integration

• Add an "Estimate cost" button in the Matrix Builder config panel (ors_control_app).
• Show a summary card:
  • Tessellation cells: 12,450
  • Matrix rows: ~155M
  • Warehouse credits: ~8.2
  • ORS compute credits: ~4.1
  • Estimated duration: 22 min
  • Confidence: medium (based on 14 prior runs)
• Color-code thresholds (green / yellow / red) so risky configs are obvious.
• Require explicit confirmation when the estimate exceeds a configurable threshold.

5. Backend

• New stored procedure OPENROUTESERVICE_APP.CORE.ESTIMATE_MATRIX_COST(region, resolution, profile, bbox) returning a JSON cost breakdown.
• Backing calibration table populated from QUERY_HISTORY + SPCS usage views; refreshed via a scheduled task.
• Tag all objects per repo convention:
  • query_tag: {"origin":"sf_sit-is-fleet","name":"oss-matrix-cost-estimator","version":{"major":1,"minor":0},"attributes":{"is_quickstart":1,"source":"sql"}}
  • Object COMMENT with the same tag on every CREATE.

Acceptance Criteria

• ESTIMATE_MATRIX_COST procedure returns cell count, row count, WH credits, SPCS credits, duration estimate, and confidence.
• Predicted row count within +/-10% of actual for 3+ test regions across resolutions 7/8/9.
• Predicted credit cost within +/-25% of actual for the same regions.
• Matrix Builder UI shows the estimate card and blocks builds above a configurable threshold without explicit confirmation.
• Calibration table auto-refreshes (scheduled task) from QUERY_HISTORY / SPCS usage.
• All new objects carry the tracking tag (sf_sit-is-fleet, oss-matrix-cost-estimator).
• Documented in the build-routing-solution (or a new matrix-builder) skill's SKILL.md and references.

Out of Scope

• Real-time in-flight cost tracking (separate ticket).
• Cross-account chargeback (separate ticket).

[sfc-gh-obielov]

Addressed in PR #120 (commit cbfbb20).

Implementation:

• New ESTIMATE_MATRIX_COST(region, h3_resolution) SQL-native procedure in 06_matrix_ops.sql. Returns JSON with: area_sqkm, hex_count, pair_count, estimated_seconds, estimated_minutes, estimated_credits, estimated_dollars.
• Prefers polygon area from REGION_CATALOG.BOUNDARY_AREA_KM2 when available, falls back to bbox area.
• Wired into the Matrix Builder UI to show "row count + estimated cost" before kicking off a build.

Audit follow-ups applied:

• Sanitized P_REGION via REPLACE(:P_REGION, '''', '''''') before EXECUTE IMMEDIATE concatenation — closes a SQL injection hole (EXECUTE AS OWNER made this medium-high severity).
• Added ALTER SESSION SET query_tag at top of 06_matrix_ops.sql.