Document the dolt_join_cost() function#74
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Closes #66. dolt_join_cost(<query>) is a planner-diagnostic scalar function (see JoinCostFuncName in go/libraries/doltcore/sqle/dfunctions/join_cost.go): it analyzes the given query and returns the join memo — the explored relation groups, the candidate physical join operators (hash/merge/ lookup/inner) and their estimated costs, with the chosen plan marked `*`. Useful for tuning joins and confirming a join hint took effect. - New `DOLT_JOIN_COST()` section under Informational Functions in dolt-sql-functions.md (with the real memo output from the engine test as the example and an explanation of the notation), plus a TOC entry. - Added it to the SQL extensions index. Intentionally NOT documenting the other function from the issue, `dolt_storage_format` — per maintainer call it's no longer relevant enough to surface. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This was referenced May 21, 2026
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Closes #66.
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dolt_join_cost(), a planner-diagnostic scalar function (join_cost.go). It takes a SQL query string, analyzes it (doesn't execute), and returns the join memo — the relation groups the planner explored, the candidate physical join operators considered for each (hash / merge / lookup / inner) and their estimated costs, with the chosen plan marked*. It's useful for tuning a slow join or confirming a join hint took effect.Changes:
DOLT_JOIN_COST()section under Informational Functions indolt-sql-functions.md, using the real memo output from dolt's engine test as the example plus an explanation of theGn/operator inputs cost/*notation. Added a matching TOC entry.sql-extensions.md).Verified:
astro buildis clean and the rendered page hasid="dolt_join_cost"with the TOC and index links resolving to it.On
dolt_storage_formatThe issue also listed
dolt_storage_format. Intentionally leaving that one undocumented — per your call it's not relevant enough anymore to surface. Closing the issue on that basis; happy to reopen/split if you'd rather track it separately.🤖 Generated with Claude Code