# How to Query Dolt Commit History for Tables Using dolt_log and dolt_history_* > Query Dolt commit history for tables using dolt_log and dolt_history_* tables. Inspect repository and table changes with standard SQL SELECT statements. - Repository: [DoltHub/dolt](https://github.com/dolthub/dolt) - Tags: how-to-guide - Published: 2026-03-14 --- **Dolt exposes every commit as queryable SQL rows through the `dolt_log` system table and `dolt_history_*` tables, allowing you to inspect repository and table-level changes using standard SELECT statements.** Dolt treats your database like a Git repository, storing every state change as a commit object that captures the entire database at a specific moment. Unlike traditional databases that overwrite data, Dolt's version-controlled architecture in the `dolthub/dolt` repository persists all historical states, making **Dolt commit history for tables** fully accessible via system tables. This guide explains how Dolt stores commit metadata and how to query it using SQL. ## How Dolt Stores Commits in the Storage Layer At the storage layer, Dolt writes commit objects as Noms values into the value store. The core routine that persists these commits lives in **[`go/store/types/value_store.go`](https://github.com/dolthub/dolt/blob/main/go/store/types/value_store.go)**, specifically the `Commit` method at line 519, which writes a new root value and a commit address (`hash.Hash`) into the object store. Commit addresses use a specific encoding defined in **[`go/store/val/codec.go`](https://github.com/dolthub/dolt/blob/main/go/store/val/codec.go)** at line 98, where the `CommitAddrEnc` field type indicates how commit references serialize into tuples. When building or reading these tuples, the system uses **[`go/store/val/tuple_builder.go`](https://github.com/dolthub/dolt/blob/main/go/store/val/tuple_builder.go)** at line 487 via `TupleBuilder.PutCommitAddr` and `TupleDesc.GetCommitAddr` to handle the low-level encoding and decoding of commit references. ## Querying Repository History with dolt_log ### The dolt_log System Table Schema The `dolt_log` table is a virtual table generated at query time that surfaces commit metadata as rows. Its schema includes: - `commit_hash`: The SHA-1-like identifier of the commit - `committer`: User who created the commit - `email`: Email address of the committer - `date`: Timestamp of the commit - `message`: Commit message - `parent_hashes`: Parent commit hashes for merge tracking ### Implementation in history_table.go The table driver implementation resides in **[`go/libraries/doltcore/sqle/history_table.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/history_table.go)**. The `rowConverter` function at line 585 maps raw commit Noms tuples into the SQL columns expected by `dolt_log`. When executing a query, the engine calls `GetRows` on this virtual table, which walks the commit DAG using the value store's `Commit` iterator built on top of the tuple descriptors that understand `CommitAddrEnc`. ## Tracking Table-Level Changes with dolt_history_* For per-table history, Dolt generates **history tables** dynamically named `dolt_history_`. These tables include all original columns from the user table plus commit metadata columns (`commit_hash`, `committer`, etc.), enabling queries like `SELECT * FROM dolt_history_orders WHERE commit_hash = 'abc123'`. The conversion logic for these table-specific histories forks from the `dolt_log` converter in **[`go/libraries/doltcore/sqle/schema_override.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/schema_override.go)** at line 164. This implementation allows you to view any row's value at any point in history using standard SQL predicates. ## Query Planning and Optimization ### Execution Plans for History Queries The SQL optimizer recognizes `dolt_log` and `dolt_history_*` as system tables. When you add an `ORDER BY` clause, the planner generates a `Sort` operator. For example, ordering by commit hash produces a plan documented in **[`go/libraries/doltcore/sqle/enginetest/dolt_query_plans.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/enginetest/dolt_query_plans.go)** at line 90: ```text Sort(dolt_log.commit_hash ASC) └─ name: dolt_log ``` ### Join Optimization with Commit Tables Queries joining diff tables with commit logs can use lookup join hints. The engine rewrites these to hash-based joins on the `commit_hash` column, as tested in **[`go/libraries/doltcore/sqle/kvexec/lookup_join_test.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/kvexec/lookup_join_test.go)** at line 136. Use the hint format: ```sql /*+ LOOKUP_JOIN(dolt_diff_xy,dolt_log) */ ``` ## Access Control and Privileges `dolt_log` enforces Dolt's privilege system. According to tests in **[`go/libraries/doltcore/sqle/enginetest/dolt_queries.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/enginetest/dolt_queries.go)** at line 1608, users without database-wide access receive errors when querying `dolt_log('main')`, while users granted explicit `SELECT` privileges can execute `SELECT COUNT(*) FROM dolt_log('main')`. ## Practical SQL Examples for Dolt Commit History ### List Recent Commits ```sql SELECT commit_hash, committer, date, message FROM dolt_log ORDER BY date DESC LIMIT 10; ``` ### Count Commits in a Specific Branch ```sql SELECT COUNT(*) FROM dolt_log('feature-branch'); ``` ### View a Table's State at a Specific Commit ```sql SELECT * FROM dolt_history_orders WHERE commit_hash = 'c3f9a2e1...' ORDER BY pk; ``` ### Find When a Specific Row Changed ```sql SELECT commit_hash, date, message FROM dolt_history_customers WHERE customer_id = 42 ORDER BY date DESC; ``` ### Combine Diffs with Commit Metadata ```sql SELECT d.from_commit, d.to_commit, l.message FROM dolt_diff_mytable AS d JOIN dolt_log AS l ON d.from_commit = l.commit_hash; ``` ## Summary - Dolt stores commits as Noms values in the value store, with addresses encoded using `CommitAddrEnc` in **[`go/store/val/codec.go`](https://github.com/dolthub/dolt/blob/main/go/store/val/codec.go)**. - The **`dolt_log`** system table exposes repository-wide commit metadata through the virtual table driver in **[`go/libraries/doltcore/sqle/history_table.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/history_table.go)**. - **Table-specific history** is available via `dolt_history_` tables, implemented in **[`go/libraries/doltcore/sqle/schema_override.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/schema_override.go)**. - Query plans for history tables support sorting and lookup joins on `commit_hash` for efficient filtering. - Access control requires explicit `SELECT` privileges on the database to query commit history. ## Frequently Asked Questions ### How do I view the commit history for a specific table in Dolt? Query the `dolt_history_` system table, which contains every row version along with commit metadata. For example, `SELECT * FROM dolt_history_users WHERE commit_hash = 'abc123'` returns the state of the `users` table at that specific commit. ### What is the difference between dolt_log and dolt_history_* tables? `dolt_log` shows repository-level commit metadata (hash, author, message) for the entire database, while `dolt_history_*` tables show row-level data changes for a specific table combined with the commit that produced each version. ### Can I join commit history tables with regular tables or diff tables? Yes, you can join `dolt_log` with diff tables using the `commit_hash` column. The optimizer supports lookup joins on these columns, and you can use hints like `/*+ LOOKUP_JOIN(dolt_diff_mytable,dolt_log) */` to optimize query performance as implemented in the engine. ### Do I need special permissions to query Dolt commit history? Yes, querying `dolt_log` requires `SELECT` privileges on the database. Users without these privileges will receive an error when attempting to query commit history, as enforced by Dolt's privilege system in **[`go/libraries/doltcore/sqle/enginetest/dolt_queries.go`](https://github.com/dolthub/dolt/blob/main/go/libraries/doltcore/sqle/enginetest/dolt_queries.go)**.