patchworks 0.3.0

Git-style visual diffs for SQLite databases. Inspect, compare, snapshot, and generate SQL migrations.
Documentation 
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//! Schema diffing for SQLite tables and columns.

use std::collections::BTreeMap;

use crate::db::types::{
    ColumnInfo, DatabaseSummary, SchemaDiff, SchemaObjectInfo, TableInfo, TableSchemaDiff,
};

/// Computes a schema diff between two inspected databases.
pub fn diff_schema(left: &DatabaseSummary, right: &DatabaseSummary) -> SchemaDiff {
    let left_tables = left
        .tables
        .iter()
        .map(|table| (table.name.clone(), table))
        .collect::<BTreeMap<_, _>>();
    let right_tables = right
        .tables
        .iter()
        .map(|table| (table.name.clone(), table))
        .collect::<BTreeMap<_, _>>();

    let mut added_tables = Vec::new();
    let mut removed_tables = Vec::new();
    let mut modified_tables = Vec::new();
    let mut unchanged_tables = Vec::new();

    for (name, right_table) in &right_tables {
        if let Some(left_table) = left_tables.get(name) {
            if let Some(diff) = diff_table_schema(left_table, right_table) {
                modified_tables.push(diff);
            } else {
                unchanged_tables.push(name.clone());
            }
        } else {
            added_tables.push((**right_table).clone());
        }
    }

    for (name, left_table) in &left_tables {
        if !right_tables.contains_key(name) {
            removed_tables.push((**left_table).clone());
        }
    }

    let (added_indexes, removed_indexes, modified_indexes) =
        diff_schema_objects(&left.indexes, &right.indexes);
    let (added_triggers, removed_triggers, modified_triggers) =
        diff_schema_objects(&left.triggers, &right.triggers);

    SchemaDiff {
        added_tables,
        removed_tables,
        modified_tables,
        unchanged_tables,
        added_indexes,
        removed_indexes,
        modified_indexes,
        added_triggers,
        removed_triggers,
        modified_triggers,
    }
}

fn diff_table_schema(left: &TableInfo, right: &TableInfo) -> Option<TableSchemaDiff> {
    let left_columns = left
        .columns
        .iter()
        .map(|column| (column.name.clone(), column))
        .collect::<BTreeMap<_, _>>();
    let right_columns = right
        .columns
        .iter()
        .map(|column| (column.name.clone(), column))
        .collect::<BTreeMap<_, _>>();

    let mut added_columns = Vec::new();
    let mut removed_columns = Vec::new();
    let mut modified_columns = Vec::new();

    for (name, right_column) in &right_columns {
        match left_columns.get(name) {
            Some(left_column) if columns_match(left_column, right_column) => {}
            Some(left_column) => {
                modified_columns.push(((**left_column).clone(), (**right_column).clone()));
            }
            None => added_columns.push((**right_column).clone()),
        }
    }

    for (name, left_column) in &left_columns {
        if !right_columns.contains_key(name) {
            removed_columns.push((**left_column).clone());
        }
    }

    if added_columns.is_empty() && removed_columns.is_empty() && modified_columns.is_empty() {
        None
    } else {
        Some(TableSchemaDiff {
            table_name: left.name.clone(),
            added_columns,
            removed_columns,
            modified_columns,
        })
    }
}

fn columns_match(left: &ColumnInfo, right: &ColumnInfo) -> bool {
    left.name == right.name
        && left.col_type.eq_ignore_ascii_case(&right.col_type)
        && left.nullable == right.nullable
        && left.default_value == right.default_value
        && left.is_primary_key == right.is_primary_key
}

fn diff_schema_objects(
    left: &[SchemaObjectInfo],
    right: &[SchemaObjectInfo],
) -> (
    Vec<SchemaObjectInfo>,
    Vec<SchemaObjectInfo>,
    Vec<(SchemaObjectInfo, SchemaObjectInfo)>,
) {
    let left_objects = left
        .iter()
        .map(|object| (object.name.clone(), object))
        .collect::<BTreeMap<_, _>>();
    let right_objects = right
        .iter()
        .map(|object| (object.name.clone(), object))
        .collect::<BTreeMap<_, _>>();

    let mut added = Vec::new();
    let mut removed = Vec::new();
    let mut modified = Vec::new();

    for (name, right_object) in &right_objects {
        match left_objects.get(name) {
            Some(left_object) if schema_objects_match(left_object, right_object) => {}
            Some(left_object) => modified.push(((**left_object).clone(), (**right_object).clone())),
            None => added.push((**right_object).clone()),
        }
    }

    for (name, left_object) in &left_objects {
        if !right_objects.contains_key(name) {
            removed.push((**left_object).clone());
        }
    }

    (added, removed, modified)
}

fn schema_objects_match(left: &SchemaObjectInfo, right: &SchemaObjectInfo) -> bool {
    left.name == right.name
        && left.table_name == right.table_name
        && left.create_sql == right.create_sql
}