feat: add dimension tables with SCD Type 2 repositories

dbt/dbt_project.yml

@@ -22,3 +22,10 @@ models:
     staging:
       +materialized: view
       +schema: staging
+    marts:
+      +materialized: table
+      +schema: marts
+
+snapshots:
+  repolytics:
+    +schema: snapshots

dbt/models/marts/_marts__models.yml

@@ -0,0 +1,45 @@
+version: 2
+
+models:
+  - name: dim_dates
+    description: Calendar dimension, one row per day (2020–2030), generated in SQL.
+    columns:
+      - name: date_key
+        description: Surrogate date key (YYYYMMDD integer).
+        data_tests: [not_null, unique]
+      - name: full_date
+        data_tests: [not_null, unique]
+
+  - name: dim_contributors
+    description: Type 1 contributor profiles aggregated across commits and pull requests.
+    columns:
+      - name: contributor_key
+        data_tests: [not_null, unique]
+      - name: username
+        data_tests: [not_null, unique]
+
+  - name: dim_repositories
+    description: SCD Type 2 repository dimension (one row per version) built on snap_repositories.
+    columns:
+      - name: repository_key
+        description: Surrogate key, hash of repository_id + the snapshot version timestamp.
+        data_tests: [not_null, unique]
+      - name: repository_id
+        data_tests: [not_null]
+      - name: is_current
+        data_tests: [not_null]
+    data_tests:
+      - dbt_utils.mutually_exclusive_ranges:
+          arguments:
+            lower_bound_column: valid_from
+            upper_bound_column: valid_to
+            partition_by: repository_id
+            gaps: not_allowed
+
+  - name: dim_labels
+    description: Type 1 dimension of distinct issue/PR labels across all projects.
+    columns:
+      - name: label_key
+        data_tests: [not_null, unique]
+      - name: label_name
+        data_tests: [not_null, unique]

dbt/models/marts/dim_contributors.sql

@@ -0,0 +1,77 @@
+-- Type 1 contributor dimension: one row per GitHub login, aggregated across the
+-- commit and pull-request staging models. Rebuilt in full each run.
+
+with commits as (
+    select
+        author_login as username,
+        repository,
+        committed_at
+    from {{ ref('stg_github__commits') }}
+    where author_login is not null
+),
+
+prs as (
+    select
+        author_login as username,
+        merged_at
+    from {{ ref('stg_github__pull_requests') }}
+    where author_login is not null
+),
+
+contributors as (
+    select username from commits
+    union
+    select username from prs
+),
+
+commit_stats as (
+    select
+        username,
+        min(committed_at::date) as first_commit_date,
+        max(committed_at::date) as last_commit_date,
+        count(*) as total_commits,
+        count(distinct repository) as distinct_projects_count
+    from commits
+    group by username
+),
+
+pr_stats as (
+    select
+        username,
+        count(*) as total_prs_opened,
+        count(*) filter (where merged_at is not null) as total_prs_merged
+    from prs
+    group by username
+),
+
+-- Most-committed-to project per contributor (ties broken alphabetically).
+primary_project as (
+    select username, repository as primary_project
+    from (
+        select
+            username,
+            repository,
+            row_number() over (
+                partition by username
+                order by count(*) desc, repository
+            ) as rn
+        from commits
+        group by username, repository
+    )
+    where rn = 1
+)
+
+select
+    {{ dbt_utils.generate_surrogate_key(['c.username']) }} as contributor_key,
+    c.username,
+    cs.first_commit_date,
+    cs.last_commit_date,
+    coalesce(cs.total_commits, 0) as total_commits,
+    coalesce(ps.total_prs_opened, 0) as total_prs_opened,
+    coalesce(ps.total_prs_merged, 0) as total_prs_merged,
+    coalesce(cs.distinct_projects_count, 0) as distinct_projects_count,
+    pp.primary_project
+from contributors c
+left join commit_stats cs on c.username = cs.username
+left join pr_stats ps on c.username = ps.username
+left join primary_project pp on c.username = pp.username

dbt/models/marts/dim_dates.sql

@@ -0,0 +1,23 @@
+with spine as (
+    {{
+        dbt_utils.date_spine(
+            datepart="day",
+            start_date="cast('2020-01-01' as date)",
+            end_date="cast('2031-01-01' as date)"
+        )
+    }}
+)
+
+select
+    cast(strftime(date_day, '%Y%m%d') as integer) as date_key,
+    cast(date_day as date) as full_date,
+    year(date_day) as year,
+    quarter(date_day) as quarter,
+    month(date_day) as month,
+    monthname(date_day) as month_name,
+    day(date_day) as day_of_month,
+    dayofweek(date_day) as day_of_week,
+    dayname(date_day) as day_name,
+    dayofweek(date_day) in (0, 6) as is_weekend,
+    week(date_day) as week_of_year
+from spine

dbt/models/marts/dim_labels.sql

@@ -0,0 +1,32 @@
+-- Type 1 label dimension: distinct issue/PR labels across all projects. Labels land
+-- in staging as a JSON array per row, so we explode the arrays and dedupe by name.
+
+with labels_raw as (
+    select labels
+    from {{ ref('stg_github__pull_requests') }}
+    where labels is not null
+    union all
+    select labels
+    from {{ ref('stg_github__issues') }}
+    where labels is not null
+),
+
+exploded as (
+    select unnest(json_extract(labels, '$[*]')) as label
+    from labels_raw
+),
+
+distinct_labels as (
+    select
+        label ->> '$.name' as label_name,
+        max(label ->> '$.color') as label_color
+    from exploded
+    where (label ->> '$.name') is not null
+    group by label ->> '$.name'
+)
+
+select
+    {{ dbt_utils.generate_surrogate_key(['label_name']) }} as label_key,
+    label_name,
+    label_color
+from distinct_labels

dbt/models/marts/dim_repositories.sql

@@ -0,0 +1,48 @@
+-- SCD Type 2 repository dimension: a thin presentation model over snap_repositories.
+-- The dbt snapshot owns the history (dbt_valid_from/to); here we reshape it into the
+-- star-schema contract (surrogate key + valid_from/valid_to/is_current).
+
+with versioned as (
+    select
+        repository_id,
+        repository_name,
+        name,
+        owner_login,
+        description,
+        stars,
+        forks,
+        open_issues,
+        language,
+        license_spdx,
+        topics,
+        created_at,
+        updated_at,
+        -- Full-resolution version timestamp drives the surrogate key so it stays
+        -- unique even if a repo changes more than once on the same calendar day;
+        -- valid_from/valid_to are kept at date grain for fact date-range joins.
+        dbt_valid_from as version_ts,
+        dbt_valid_from::date as valid_from,
+        coalesce(dbt_valid_to::date, date '9999-12-31') as valid_to,
+        dbt_valid_to is null as is_current
+    from {{ ref('snap_repositories') }}
+)
+
+select
+    {{ dbt_utils.generate_surrogate_key(['repository_id', 'version_ts']) }} as repository_key,
+    repository_id,
+    repository_name,
+    name,
+    owner_login,
+    description,
+    stars,
+    forks,
+    open_issues,
+    language,
+    license_spdx,
+    topics,
+    created_at,
+    updated_at,
+    valid_from,
+    valid_to,
+    is_current
+from versioned

dbt/snapshots/snap_repositories.sql

@@ -0,0 +1,14 @@
+{% snapshot snap_repositories %}
+
+{{
+    config(
+        unique_key='repository_id',
+        strategy='check',
+        check_cols=['stars', 'forks', 'open_issues', 'description', 'topics'],
+    )
+}}
+
+-- SCD Type 2 history capture for repositories.
+select * from {{ ref('stg_github__repositories') }}
+
+{% endsnapshot %}

dbt/tests/assert_dim_date_completeness.sql

@@ -0,0 +1,14 @@
+-- Fails if consecutive days in dim_dates are not exactly one day apart, i.e. the
+-- generated date dimension has a gap. Passes when zero rows are returned.
+
+with ordered as (
+    select
+        full_date,
+        lead(full_date) over (order by full_date) as next_date
+    from {{ ref('dim_dates') }}
+)
+
+select *
+from ordered
+where next_date is not null
+  and next_date <> full_date + 1