Add indexes to a Postgres table with 500k rows. Queries filtering by user_id and created_at are slow; create appropriate indexes to meet latency targets.
Our orders table is really slow when we filter by user or date. Can you add some indexes to speed it up?
Let me find the orders table definition in the codebase.
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{
"type": "tool_reference",
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}Let me find the orders table definition first.
{"pattern":"orders","glob":"*.sql"}{"pattern":"**/*.sql"}Ripgrep search timed out after 20 seconds. The search may have matched files but did not complete in time. Try searching a more specific path or pattern.
Found 3 files workspace/queries/q2.sql workspace/queries/q1.sql scenario/init/postgres-setup.sql
{"query":"select:Read","max_results":1}{
"type": "tool_reference",
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}{"file_path":"/scenario/init/postgres-setup.sql"}{"file_path":"/workspace/queries/q1.sql"}{"file_path":"/workspace/queries/q2.sql"} 1→CREATE SCHEMA IF NOT EXISTS app;
2→
3→CREATE TABLE app.orders (
4→ order_id SERIAL PRIMARY KEY,
5→ user_id TEXT NOT NULL,
6→ created_at TIMESTAMPTZ NOT NULL,
7→ amount NUMERIC(10, 2) NOT NULL
8→);
9→
10→INSERT INTO app.orders... 1→SELECT * FROM app.orders WHERE user_id = 'user_42' ORDER BY created_at DESC LIMIT 10
2→ 1→SELECT * FROM app.orders WHERE created_at >= '2025-02-01' AND created_at < '2025-03-01' ORDER BY created_at
2→The table has 500k rows with no indexes beyond the primary key. The two queries filter by `user_id` and `created_at` respectively. Let me add indexes to cover both.
{"query":"select:Write","max_results":1}{
"type": "tool_reference",
"tool_name": "Write"
}{"file_path":"/workspace/solution.sql","content":"CREATE INDEX idx_orders_user_id ON app.orders (user_id, created_at DESC);\nCREATE INDEX idx_orders_created_at ON app.orders (created_at);\n"}File created successfully at: /workspace/solution.sql
Now let me verify it works against the database.
{"command":"psql -U postgres -f /workspace/solution.sql 2>&1","description":"Create indexes on the orders table"}CREATE INDEX CREATE INDEX
Let me verify the indexes exist and that they're being used by the queries.
{"command":"psql -U postgres -c \"EXPLAIN ANALYZE $(cat /workspace/queries/q1.sql);\" 2>&1","description":"Check query plan for user_id filter query"}{"command":"psql -U postgres -c \"EXPLAIN ANALYZE $(cat /workspace/queries/q2.sql);\" 2>&1","description":"Check query plan for date range filter query"}QUERY PLAN ---------------------------------------------------------------------------------------------------------------------------------------- Limit...
QUERY PLAN -----------------------------------------------------------------------------------------------------------------------------...
Both indexes are working. Here's what was added in `/workspace/solution.sql`: 1. **`idx_orders_user_id`** on `(user_id, created_at DESC)` — A composite index that covers the `q1.sql` query filtering by `user_id` and ordering by `created_at DESC`. PostgreSQL can satisfy both the ...
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"content": "Our orders table is really slow when we filter by user or date. Can you add some indexes to speed it up?"
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"content": " 1→CREATE SCHEMA IF NOT EXISTS app;\n 2→\n 3→CREATE TABLE app.orders (\n 4→ order_id SERIAL PRIMARY KEY,\n 5→ user_id TEXT NOT NULL,\n 6→ created_at TIMESTAMPTZ NOT NULL,\n 7→ amount NUMERIC(10, 2) NOT NULL\n 8→);\n 9→\n 10→INSERT INTO app.orders (user_id, created_at, amount)\n 11→SELECT\n 12→ 'user_' || (random() * 1000)::int,\n 13→ '2025-01-01'::timestamptz + (random() * interval '90 days'),\n 14→ (random() * 1000)::numeric(10, 2)\n 15→FROM generate_series(1, 500000);\n 16→"
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"content": " 1→SELECT * FROM app.orders WHERE user_id = 'user_42' ORDER BY created_at DESC LIMIT 10\n 2→"
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"content": " 1→SELECT * FROM app.orders WHERE created_at >= '2025-02-01' AND created_at < '2025-03-01' ORDER BY created_at\n 2→"
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"content": "The table has 500k rows with no indexes beyond the primary key. The two queries filter by `user_id` and `created_at` respectively. Let me add indexes to cover both."
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"content": "CREATE INDEX idx_orders_user_id ON app.orders (user_id, created_at DESC);\nCREATE INDEX idx_orders_created_at ON app.orders (created_at);\n"
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"content": "File created successfully at: /workspace/solution.sql"
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"content": "Now let me verify it works against the database."
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"description": "Create indexes on the orders table"
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"content": "CREATE INDEX\nCREATE INDEX"
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"content": "Let me verify the indexes exist and that they're being used by the queries."
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"description": "Check query plan for user_id filter query"
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"command": "psql -U postgres -c \"EXPLAIN ANALYZE $(cat /workspace/queries/q2.sql);\" 2>&1",
"description": "Check query plan for date range filter query"
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"content": " QUERY PLAN \n----------------------------------------------------------------------------------------------------------------------------------------\n Limit (cost=0.42..38.33 rows=10 width=26) (actual time=3.919..4.055 rows=10 loops=1)\n -> Index Scan using idx_orders_user_id on orders (cost=0.42..1877.02 rows=495 width=26) (actual time=3.918..4.052 rows=10 loops=1)\n Index Cond: (user_id = 'user_42'::text)\n Planning Time: 2.959 ms\n Execution Time: 4.500 ms\n(5 rows)"
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"isError": false,
"content": " QUERY PLAN \n----------------------------------------------------------------------------------------------------------------------------------------------------------\n Index Scan using idx_orders_created_at on orders (cost=0.42..19495.08 rows=154354 width=26) (actual time=1.158..240.815 rows=155440 loops=1)\n Index Cond: ((created_at >= '2025-02-01 00:00:00+00'::timestamp with time zone) AND (created_at < '2025-03-01 00:00:00+00'::timestamp with time zone))\n Planning Time: 0.920 ms\n Execution Time: 244.606 ms\n(4 rows)"
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"content": "Both indexes are working. Here's what was added in `/workspace/solution.sql`:\n\n1. **`idx_orders_user_id`** on `(user_id, created_at DESC)` — A composite index that covers the `q1.sql` query filtering by `user_id` and ordering by `created_at DESC`. PostgreSQL can satisfy both the filter and the sort directly from the index.\n\n2. **`idx_orders_created_at`** on `(created_at)` — Covers the `q2.sql` query that filters by a date range and orders by `created_at`.\n\nBoth queries now use **Index Scans** instead of sequential scans across the 500k-row table."
}
]
}Debugging Output
6 files · 49KBHarness
base-rt
Agent
claude-code
Model
claude-opus-4-6
Version
v0.1.0
Persona
naive
Plan Mode
no-plan
Prompt
Unknown
Our orders table is really slow when we filter by user or date. Can you add some indexes to speed it up?
ID
foo-bar-postgres-index-tuning
Domain
foo-bar
Tier
tier-1
Harness
base-rt
Postgres with app.orders (500k rows). No indexes on user_id or created_at; queries in /workspace/queries/ are slow.
Create indexes on app.orders for user_id and created_at so the slow queries in /workspace/queries/ run under 50ms.