Rewrite Engine

Isofold rewrites your SQL queries to make them cheaper—without changing what they do. We apply a suite of optimizer rules using Apache DataFusion that are tested against real-world analytical workloads (like the Google Ethereum dataset). Each rewrite rule:

Preserves semantics
Targets measurable inefficiencies
Composes cleanly with others

How It Works

The incoming SQL is parsed into a logical plan.
Isofold applies rewrite rules in a deterministic order.
Both original and rewritten queries are dry-run for:
- Logical plan structure
- Slot usage / bytes scanned
- Compatibility with warehouse constraints
If the rewritten query is valid and cheaper, it is executed.
Otherwise, Isofold automatically falls back to the original.

Examples

`PushDownFilter`

-- Original
SELECT COUNT(*)
FROM (
    SELECT *
    FROM `bigquery-public-data.crypto_ethereum.transactions`
    WHERE to_address = '0x742d35Cc6634C0532925a3b844Bc454e4438f44e'
)

-- Rewritten
SELECT COUNT(*)
FROM `bigquery-public-data.crypto_ethereum.transactions`
WHERE to_address = '0x742d35Cc6634C0532925a3b844Bc454e4438f44e'

`PushDownLimit`

-- Original
WITH top_blocks AS (
    SELECT *
    FROM `bigquery-public-data.crypto_ethereum.blocks`
    ORDER BY difficulty DESC
)
SELECT miner
FROM top_blocks
LIMIT 5

-- Rewritten
SELECT miner
FROM (
    SELECT *
    FROM `bigquery-public-data.crypto_ethereum.blocks`
    ORDER BY difficulty DESC
    LIMIT 5
)

`ProjectionPrune` + `OptimizeProjections`

-- Original
SELECT COUNT(*)
FROM (
    SELECT *
    FROM `bigquery-public-data.crypto_ethereum.transactions`
)

-- Rewritten
SELECT COUNT(*)
FROM (
    SELECT 1
    FROM `bigquery-public-data.crypto_ethereum.transactions`
)

`SimplifyExpressions`

-- Original
SELECT *,
    CASE
        WHEN status = 'confirmed' THEN TRUE
        WHEN status != 'confirmed' THEN FALSE
        ELSE TRUE
    END AS is_finalized
FROM `bigquery-public-data.crypto_ethereum.transactions`
WHERE DATE(block_timestamp) >= '2023-01-01'
    AND TRUE OR TRUE

-- Rewritten
SELECT *,
    status = 'confirmed' AS is_finalized
FROM `bigquery-public-data.crypto_ethereum.transactions`
WHERE DATE(block_timestamp) >= '2023-01-01'

`EliminateDuplicatedExpr`

-- Original
SELECT value / 1e18 AS eth_value,
       value / 1e18 AS normalized
FROM `bigquery-public-data.crypto_ethereum.traces`

-- Rewritten
SELECT value / 1e18 AS eth_value,
       eth_value AS normalized
FROM `bigquery-public-data.crypto_ethereum.traces`

`EliminateFilter`

-- Original
SELECT *
FROM `bigquery-public-data.crypto_ethereum.tokens`
WHERE TRUE

-- Rewritten
SELECT *
FROM `bigquery-public-data.crypto_ethereum.tokens`

`EliminateGroupByConstant`

-- Original
SELECT token_address, COUNT(*)
FROM `bigquery-public-data.crypto_ethereum.token_transfers`
GROUP BY token_address, 'erc20'

-- Rewritten
SELECT token_address, COUNT(*)
FROM `bigquery-public-data.crypto_ethereum.token_transfers`
GROUP BY token_address

`EliminateJoin`

-- Original
SELECT b.block_number
FROM `bigquery-public-data.crypto_ethereum.blocks` b
    LEFT JOIN `bigquery-public-data.crypto_ethereum.transactions` t
        ON b.number = t.block_number

-- Rewritten
SELECT block_number
FROM `bigquery-public-data.crypto_ethereum.blocks`

`EliminateLimit`

-- Original
SELECT COUNT(*)
FROM (
    SELECT *
    FROM `bigquery-public-data.crypto_ethereum.transactions`
    LIMIT 10000
)

-- Rewritten
SELECT COUNT(*)
FROM `bigquery-public-data.crypto_ethereum.transactions`

`EliminateNestedUnion` / `EliminateOneUnion`

-- Original
SELECT *
FROM (
    SELECT * FROM tx1
    UNION ALL
    SELECT * FROM tx2
)
WHERE block_number > 1000000

-- Rewritten
SELECT *
FROM tx1
WHERE block_number > 1000000
UNION ALL
SELECT *
FROM tx2
WHERE block_number > 1000000

`EliminateOuterJoin`

-- Original
SELECT *
FROM a
    LEFT JOIN b
        ON a.id = b.id
WHERE b.id IS NOT NULL

-- Rewritten
SELECT *
FROM a
    JOIN b
        ON a.id = b.id

`ExtractEquijoinPredicate`

-- Original
SELECT *
FROM a, b
WHERE a.id = b.id
    AND b.confirmed = TRUE

-- Rewritten
SELECT *
FROM a
    JOIN b
        ON a.id = b.id
WHERE b.confirmed = TRUE

`FilterNullJoinKeys`

-- Rewritten
SELECT *
FROM a
    JOIN b
        ON a.key = b.key
WHERE a.key IS NOT NULL
    AND b.key IS NOT NULL

`ReplaceDistinctWithAggregate`

-- Original
SELECT DISTINCT from_address
FROM `bigquery-public-data.crypto_ethereum.transactions`

-- Rewritten
SELECT from_address
FROM `bigquery-public-data.crypto_ethereum.transactions`
GROUP BY from_address

`ScalarSubqueryToJoin`

-- Original
SELECT t.hash,
    (
        SELECT MAX(value)
        FROM `bigquery-public-data.crypto_ethereum.transactions` t2
        WHERE t2.to_address = t.to_address
    ) AS max_val
FROM `bigquery-public-data.crypto_ethereum.transactions` t

-- Rewritten
SELECT t.hash,
       MAX(t2.value) AS max_val
FROM `bigquery-public-data.crypto_ethereum.transactions` t
    JOIN `bigquery-public-data.crypto_ethereum.transactions` t2
        ON t.to_address = t2.to_address
GROUP BY t.hash

`SingleDistinctToGroupBy`

-- Original
SELECT DISTINCT token_address
FROM `bigquery-public-data.crypto_ethereum.token_transfers`

-- Rewritten
SELECT token_address
FROM `bigquery-public-data.crypto_ethereum.token_transfers`
GROUP BY token_address

Composed Rewrite:

-- Original
SELECT DISTINCT t.from_address,
       COUNT(*) as tx_count
FROM (
    SELECT *
    FROM `bigquery-public-data.crypto_ethereum.transactions`
    WHERE status = 'confirmed'
) t
    LEFT JOIN (
        SELECT *
        FROM `bigquery-public-data.crypto_ethereum.blocks`
    ) b
        ON t.block_number = b.number
WHERE b.number IS NOT NULL
GROUP BY t.from_address, 'eth'
LIMIT 1000000

-- Rewritten
SELECT from_address,
       COUNT(*) AS tx_count
FROM `bigquery-public-data.crypto_ethereum.transactions` t
    JOIN `bigquery-public-data.crypto_ethereum.blocks` b
        ON t.block_number = b.number
WHERE t.status = 'confirmed'
GROUP BY from_address

Applied Rules:

PushDownFilter
SimplifyExpressions
EliminateOuterJoin
ProjectionPrune
EliminateGroupByConstant
ReplaceDistinctWithAggregate
EliminateLimit

Guarantees

Dry-run validated for correctness
Cost-estimated before execution
Fallback-safe: if a rewrite introduces cost or fails validation, Isofold reverts to the original

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How It Works

Examples

`PushDownFilter`

`PushDownLimit`

`ProjectionPrune` + `OptimizeProjections`

`SimplifyExpressions`

`EliminateDuplicatedExpr`

`EliminateFilter`

`EliminateGroupByConstant`

`EliminateJoin`

`EliminateLimit`

`EliminateNestedUnion` / `EliminateOneUnion`

`EliminateOuterJoin`

`ExtractEquijoinPredicate`

`FilterNullJoinKeys`

`ReplaceDistinctWithAggregate`

`ScalarSubqueryToJoin`

`SingleDistinctToGroupBy`

Composed Rewrite:

Guarantees

​How It Works

​Examples

​PushDownFilter

​PushDownLimit

​ProjectionPrune + OptimizeProjections

​SimplifyExpressions

​EliminateDuplicatedExpr

​EliminateFilter

​EliminateGroupByConstant

​EliminateJoin

​EliminateLimit

​EliminateNestedUnion / EliminateOneUnion

​EliminateOuterJoin

​ExtractEquijoinPredicate

​FilterNullJoinKeys

​ReplaceDistinctWithAggregate

​ScalarSubqueryToJoin

​SingleDistinctToGroupBy

​Composed Rewrite:

​Guarantees

How It Works

Examples

`PushDownFilter`

`PushDownLimit`

`ProjectionPrune` + `OptimizeProjections`

`SimplifyExpressions`

`EliminateDuplicatedExpr`

`EliminateFilter`

`EliminateGroupByConstant`

`EliminateJoin`

`EliminateLimit`

`EliminateNestedUnion` / `EliminateOneUnion`

`EliminateOuterJoin`

`ExtractEquijoinPredicate`

`FilterNullJoinKeys`

`ReplaceDistinctWithAggregate`

`ScalarSubqueryToJoin`

`SingleDistinctToGroupBy`

Composed Rewrite:

Guarantees