CSharpDB v2.9.1

v2.9.0

Planner Statistics and Durable Write Batching

• Added the next phase of statistics-guided planning with richer ANALYZE data, including histogram, heavy-hitter, and composite-prefix statistics used by the optimizer for better cardinality and join-cost estimates.
• Extended the planner to use bounded dynamic-programming join reordering on qualifying inner-join chains instead of relying only on simpler greedy choices.
• Added durable-write batching infrastructure and shared storage copy batching so WAL- and maintenance-adjacent copy paths can batch work more efficiently without changing default durability semantics.
• Added explicit sys.table_stats.row_count_is_exact semantics so planner costing can distinguish estimated row counts from exact counts and keep COUNT(*) fast paths honest.

Planner and Runtime Stabilization

• Followed the main optimizer/storage work with stabilization updates across planner, checkpoint, and maintenance behavior after merge-time regressions surfaced in tests.
• Tightened planner behavior around batch evaluation, join planning, and checkpoint-related validation to keep the new stats-guided and batching paths correct under the existing test suite.
• Restored cache-hot covered composite-index lookup performance by exposing cache-only reads from the default B-tree index store and adding a direct planner fast path for exact covered composite projections, bringing the focused composite benchmark rows back ahead of baseline.
• Added and refreshed regression coverage across planner statistics, WAL behavior, integration scenarios, page-read buffering, and hybrid/local database paths.

CLI Console Experience

• Migrated CSharpDB.Cli from the handwritten ANSI output layer to Spectre.Console so the shell, help text, query tables, schema panels, and status messages render with a more consistent console UI.
• Added a shared CliConsole helper with the new ASCII startup banner, left-anchored branding, richer prompt/status rendering, and reusable table/panel helpers for CLI commands.
• Added an interactive dot-command menu at the csdb> prompt. Pressing . as the first character at a fresh prompt now opens a keyboard-driven menu of supported dot commands with Up/Down, Enter, and Esc.
• Hardened the dot-command menu renderer so it clamps itself to the console buffer and scrolls the visible command window instead of crashing near the bottom of the terminal.

Documentation Refresh

• Added contributor-facing documentation for configuration, the query execution pipeline, SQL surface behavior, and combined query/durable-write performance guidance.
• Refreshed the roadmap to reflect the current v2.9.0 status of the optimizer, batch execution, and durable-write work.
• Validated the branch with dotnet build CSharpDB.slnx, dotnet build src/CSharpDB.Cli/CSharpDB.Cli.csproj, dotnet test tests/CSharpDB.Cli.Tests/CSharpDB.Cli.Tests.csproj, and dotnet test CSharpDB.slnx.