Index effectiveness analysis

Answers "do the ORDER BY key, skipping indexes and projections match what the queries actually filter on?" from system.data_skipping_indices, system.projections, system.tables, system.parts and the ProfileEvents in system.query_log. Run altinity-expert-clickhouse-connection first if the connection mode, cluster and time window are not yet established.

Query packs

• checks.sql — 10 checks: skipping index inventory (index-analysis-01), projections and their ORDER BY keys (index-analysis-02, needs system.projections), top tables by query frequency (index-analysis-03), queries with poor granule selectivity (index-analysis-04), frequently filtered columns (index-analysis-05), primary key columns with part and PK-memory aggregates (index-analysis-06), skip index size versus column size (index-analysis-07), queries that bypass the primary key (index-analysis-08), partition pruning effectiveness (index-analysis-09), WHERE condition patterns per table (index-analysis-10).
• reference.md — background (ORDER BY design guidelines, anti-patterns, skipping index selection); read only when you need to explain a recommendation.

How to run the query packs

1. Read each pack file from this skill's directory (the skill loader prints the directory path).
2. Run statements one at a time, never a whole file. Statements end with ; and start with a -- @check <id> <title> header; keep the id with its result.
3. Honor -- @requires: skip the statement when the named table is missing, when keeper is required and the server has no Keeper/ZooKeeper, or when the version condition is not met. List skipped ids with the reason.
4. Keep {cluster} as written when a cluster macro exists; otherwise apply the connection skill's rewrite rule. Any other {placeholder} is a template variable: substitute a real value first or skip the statement.
5. On an error, record the check id and the first line of the error, then continue. Only for UNKNOWN_IDENTIFIER, run DESCRIBE TABLE system.<table> and drop the missing column.
6. A severity column is the verdict for that row. Copy it; do not re-grade.