fix(query,types): refactor Row to Value-typed map, fix IN list, nkPath, multi-table joins

- Refactored Row from Table[string, string] to Table[string, Value]
- Added Value operators: ==, !=, $, in for string interop
- Fixed valueToString for vkNull to return '\\N' instead of ''
- Fixed evalExpr irekField to return vkNull when field not found
- Added IN (val1, val2, ...) parser support
- Fixed nkPath column names in multi-table joins
- Fixed LATERAL JOIN null padding when no matching rows
- Added CREATE/DROP/USE/SHOW DATABASE parser support
- Adapted all tests for new Value type

src/barabadb/core/httpserver.nim

@@ -6,13 +6,13 @@ import hunos/context
 import json
 import tables
 import strutils
-import os
 import times
 import std/asyncdispatch
 import config
 import ../query/lexer
 import ../query/parser
 import ../query/executor
+import ../core/types
 import ../storage/lsm
 import ../core/mvcc
 import ../protocol/wire
@@ -20,6 +20,7 @@ import ../core/websocket
 import jwt as jwtlib
 import ../protocol/auth
 import ../protocol/ratelimit
+import ../core/registry
 
 type
   HttpServer* = ref object
@@ -27,6 +28,7 @@ type
     running: bool
     db*: LSMTree
     ctx: ExecutionContext
+    registry*: DatabaseRegistry
     metrics*: Metrics
     secretKey*: string
     authManager*: AuthManager
@@ -40,8 +42,10 @@ type
     selectCount*: int
     activeConnections*: int
 
-proc newHttpServerWithDb*(config: BaraConfig, db: LSMTree): HttpServer =
-  let ctx = newExecutionContext(db)
+proc newHttpServerWithRegistry*(config: BaraConfig, registry: DatabaseRegistry): HttpServer =
+  let dbInfo = getOrCreateDatabase(registry, "default")
+  let db = dbInfo.db
+  let ctx = cast[ExecutionContext](cast[pointer](dbInfo.ctx))
   ctx.txnManager = newTxnManager()
   let secret = config.getEffectiveJwtSecret()
   let ws = newWsServer(config, secret)
@@ -51,15 +55,27 @@ proc newHttpServerWithDb*(config: BaraConfig, db: LSMTree): HttpServer =
     asyncCheck ws.broadcastToTable(ev.table, msg)
   let am = newAuthManager(secret)
   HttpServer(config: config, running: false, db: db, ctx: ctx,
+             registry: registry,
              secretKey: secret,
              authManager: am,
              rateLimiter: rl,
              metrics: Metrics(), ws: ws)
 
+proc newHttpServerWithDb*(config: BaraConfig, db: LSMTree): HttpServer =
+  let registry = newDatabaseRegistry(config)
+  registry.setContextFactory(proc(d: LSMTree, r: DatabaseRegistry): ContextRef {.closure.} =
+    cast[ContextRef](cast[pointer](newExecutionContext(d, r))))
+  let ctx = newExecutionContext(db, registry)
+  registry.setDatabase("default", db, cast[ContextRef](cast[pointer](ctx)))
+  return newHttpServerWithRegistry(config, registry)
+
 proc newHttpServer*(config: BaraConfig): HttpServer =
-  let dataDir = config.dataDir / "server"
-  let db = newLSMTree(dataDir)
-  return newHttpServerWithDb(config, db)
+  let registry = newDatabaseRegistry(config)
+  registry.setContextFactory(proc(d: LSMTree, r: DatabaseRegistry): ContextRef {.closure.} =
+    cast[ContextRef](cast[pointer](newExecutionContext(d, r))))
+  registry.loadExistingDatabases()
+  registry.ensureDefaultDatabase()
+  return newHttpServerWithRegistry(config, registry)
 
 # ----------------------------------------------------------------------
 # JWT helpers
@@ -178,8 +194,8 @@ proc queryHandler(server: HttpServer): RequestHandler =
           var jsonRow = newJObject()
           for col in res.columns:
             let key = col
-            if key in row and not isNull(row[key]):
-              jsonRow[key] = %row[key]
+            if key in row and row[key].kind != vkNull:
+              jsonRow[key] = %valueToString(row[key])
             else:
               jsonRow[key] = newJNull()
           jsonRows.add(jsonRow)
@@ -564,4 +580,7 @@ proc run*(server: HttpServer, port: int = 9470) =
 proc stop*(server: HttpServer) =
   server.running = false
   server.ws.stop()
-  server.db.close()
+  if server.registry != nil:
+    server.registry.closeAll()
+  else:
+    server.db.close()

src/barabadb/core/registry.nim

@@ -0,0 +1,192 @@
+## BaraDB Database Registry — manages per-database LSMTree instances
+import std/tables
+import std/os
+import std/strutils
+import std/locks
+import std/algorithm
+import logging
+import config
+import ../storage/lsm
+
+type
+  ContextRef* = ref RootObj
+
+  ContextFactory* = proc(db: LSMTree, reg: DatabaseRegistry): ContextRef {.closure.}
+
+  DatabaseInfo* = ref object
+    name*: string
+    db*: LSMTree
+    ctx*: ContextRef
+    activeConnections*: int
+
+  DatabaseRegistry* = ref object
+    config*: BaraConfig
+    databases: Table[string, DatabaseInfo]
+    lock*: Lock
+    defaultDbName*: string
+    dataRoot*: string
+    ctxFactory*: ContextFactory
+
+const reservedDbNames* = ["system", "information_schema", "pg_catalog"]
+
+proc isValidDbName*(name: string): bool =
+  if name.len == 0: return false
+  if '/' in name or '\\' in name: return false
+  if name in reservedDbNames: return false
+  if name.startsWith("_"): return false
+  if name == ".." or name == ".": return false
+  true
+
+proc newDatabaseRegistry*(config: BaraConfig, defaultDbName = "default"): DatabaseRegistry =
+  new(result)
+  result.config = config
+  result.databases = initTable[string, DatabaseInfo]()
+  result.defaultDbName = defaultDbName
+  result.dataRoot = config.dataDir / "databases"
+  initLock(result.lock)
+
+  # Create root directory
+  if not dirExists(result.dataRoot):
+    createDir(result.dataRoot)
+
+proc setContextFactory*(reg: DatabaseRegistry, factory: ContextFactory) =
+  reg.ctxFactory = factory
+
+proc loadExistingDatabases*(reg: DatabaseRegistry) =
+  if reg.ctxFactory == nil:
+    raise newException(ValueError, "Context factory not set. Call setContextFactory first.")
+
+  # Scan for existing databases
+  for kind, path in walkDir(reg.dataRoot):
+    if kind == pcDir:
+      let dbName = path.splitPath().tail
+      if dbName.len > 0 and isValidDbName(dbName):
+        let dbDir = reg.dataRoot / dbName
+        info("Loading database '" & dbName & "' from " & dbDir)
+        let db = newLSMTree(dbDir)
+        let ctx = reg.ctxFactory(db, reg)
+        reg.databases[dbName] = DatabaseInfo(
+          name: dbName, db: db, ctx: ctx, activeConnections: 0
+        )
+
+proc setDatabase*(reg: DatabaseRegistry, name: string, db: LSMTree, ctx: ContextRef) =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  reg.databases[name] = DatabaseInfo(
+    name: name, db: db, ctx: ctx, activeConnections: 0)
+
+proc ensureDefaultDatabase*(reg: DatabaseRegistry) =
+  if reg.ctxFactory == nil:
+    raise newException(ValueError, "Context factory not set. Call setContextFactory first.")
+
+  let defaultDbName = reg.defaultDbName
+  if defaultDbName notin reg.databases:
+    let dbDir = reg.dataRoot / defaultDbName
+    info("Creating default database at " & dbDir)
+    let db = newLSMTree(dbDir)
+    let ctx = reg.ctxFactory(db, reg)
+    reg.databases[defaultDbName] = DatabaseInfo(
+      name: defaultDbName, db: db, ctx: ctx, activeConnections: 0
+    )
+
+proc getOrCreateDatabase*(reg: DatabaseRegistry, name: string): DatabaseInfo =
+  if not isValidDbName(name):
+    raise newException(ValueError, "Invalid database name: " & name)
+
+  if reg.ctxFactory == nil:
+    raise newException(ValueError, "Context factory not set. Call setContextFactory first.")
+
+  acquire(reg.lock)
+  defer: release(reg.lock)
+
+  if name in reg.databases:
+    return reg.databases[name]
+
+  # Create new database
+  let dbDir = reg.dataRoot / name
+  info("Creating database '" & name & "' at " & dbDir)
+  let db = newLSMTree(dbDir)
+  let ctx = reg.ctxFactory(db, reg)
+  let info = DatabaseInfo(name: name, db: db, ctx: ctx, activeConnections: 0)
+  reg.databases[name] = info
+  info
+
+proc getConnectionCount*(reg: DatabaseRegistry, name: string): int =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  if name in reg.databases:
+    return reg.databases[name].activeConnections
+  return 0
+
+proc incrementConnections*(reg: DatabaseRegistry, name: string) =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  if name in reg.databases:
+    inc reg.databases[name].activeConnections
+
+proc decrementConnections*(reg: DatabaseRegistry, name: string) =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  if name in reg.databases and reg.databases[name].activeConnections > 0:
+    dec reg.databases[name].activeConnections
+
+proc dropDatabase*(reg: DatabaseRegistry, name: string): bool =
+  if not isValidDbName(name):
+    return false
+
+  acquire(reg.lock)
+  defer: release(reg.lock)
+
+  if name notin reg.databases:
+    return false
+
+  if name == reg.defaultDbName:
+    raise newException(ValueError, "Cannot drop the default database")
+
+  let info = reg.databases[name]
+  if info.activeConnections > 0:
+    raise newException(ValueError,
+      "Cannot drop database '" & name & "': " &
+      $info.activeConnections & " active connections")
+
+  # Close LSMTree
+  info.db.close()
+
+  # Remove data directory
+  let dbDir = reg.dataRoot / name
+  if dirExists(dbDir):
+    removeDir(dbDir)
+
+  reg.databases.del(name)
+  true
+
+proc listDatabases*(reg: DatabaseRegistry): seq[string] =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  result = @[]
+  for name in reg.databases.keys:
+    result.add(name)
+  result.sort()
+
+proc databaseExists*(reg: DatabaseRegistry, name: string): bool =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  name in reg.databases
+
+proc getDatabaseInfo*(reg: DatabaseRegistry, name: string): DatabaseInfo =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  if name in reg.databases:
+    return reg.databases[name]
+  return nil
+
+proc closeAll*(reg: DatabaseRegistry) =
+  acquire(reg.lock)
+  defer: release(reg.lock)
+  for name, info in reg.databases.pairs:
+    try:
+      info.db.close()
+      info("Database '" & name & "' closed")
+    except CatchableError as e:
+      warn("Error closing database '" & name & "': " & e.msg)
+  reg.databases.clear()

src/barabadb/core/server.nim

@@ -4,7 +4,6 @@ import std/asyncnet
 import std/strutils
 import std/sequtils
 import std/tables
-import std/os
 import std/endians
 import std/monotimes
 import std/locks
@@ -28,6 +27,7 @@ import ../core/replication
 import ../core/sharding
 import ../core/gossip
 import ../protocol/ratelimit
+import ../core/registry
 import jwt as jwtlib
 
 type
@@ -36,6 +36,7 @@ type
     running*: bool
     db*: LSMTree
     ctx*: ExecutionContext
+    registry*: DatabaseRegistry
     txnManager*: TxnManager
     distTxnManager*: DistTxnManager
     replicationManager*: ReplicationManager
@@ -47,8 +48,10 @@ type
     activeConnections*: int
     activeConnectionsLock*: Lock
 
-proc newServerWithDb*(config: BaraConfig, db: LSMTree): Server =
-  let ctx = newExecutionContext(db)
+proc newServerWithRegistry*(config: BaraConfig, registry: DatabaseRegistry): Server =
+  let dbInfo = getOrCreateDatabase(registry, "default")
+  let db = dbInfo.db
+  let ctx = cast[ExecutionContext](cast[pointer](dbInfo.ctx))
   ctx.txnManager = newTxnManager()
   var tls: TLSContext = nil
   if config.tlsEnabled and config.certFile.len > 0 and config.keyFile.len > 0:
@@ -60,7 +63,7 @@ proc newServerWithDb*(config: BaraConfig, db: LSMTree): Server =
   let localId = if config.raftNodeId.len > 0: config.raftNodeId else: "node-" & $config.port
   let cm = newClusterMembership(shardRouter, localId)
 
-  # Wire shard migration callbacks to LSM
+  # Wire shard migration callbacks to LSM (use default database)
   shardRouter.iterateKeys = proc(shardId: int): seq[(string, seq[byte])] {.gcsafe.} =
     var entries: seq[(string, seq[byte])] = @[]
     for (key, value) in db.scanAll():
@@ -94,6 +97,7 @@ proc newServerWithDb*(config: BaraConfig, db: LSMTree): Server =
   let rl = newRateLimiter(rlaTokenBucket, config.rateLimitGlobal, config.rateLimitPerClient)
 
   result = Server(config: config, running: false, db: db, ctx: ctx,
+         registry: registry,
          txnManager: ctx.txnManager, distTxnManager: newDistTxnManager(),
          replicationManager: newReplicationManager(),
          shardRouter: shardRouter,
@@ -103,10 +107,22 @@ proc newServerWithDb*(config: BaraConfig, db: LSMTree): Server =
          rateLimiter: rl)
   initLock(result.activeConnectionsLock)
 
+proc newServerWithDb*(config: BaraConfig, db: LSMTree): Server =
+  let registry = newDatabaseRegistry(config)
+  let ctx = newExecutionContext(db, registry)
+  registry.setContextFactory(proc(d: LSMTree, r: DatabaseRegistry): ContextRef {.closure.} =
+    cast[ContextRef](cast[pointer](newExecutionContext(d, r))))
+  # Use the existing db for default
+  registry.setDatabase("default", db, cast[ContextRef](cast[pointer](ctx)))
+  return newServerWithRegistry(config, registry)
+
 proc newServer*(config: BaraConfig): Server =
-  let dataDir = config.dataDir / "server"
-  let db = newLSMTree(dataDir)
-  return newServerWithDb(config, db)
+  let registry = newDatabaseRegistry(config)
+  registry.setContextFactory(proc(d: LSMTree, r: DatabaseRegistry): ContextRef {.closure.} =
+    cast[ContextRef](cast[pointer](newExecutionContext(d, r))))
+  registry.loadExistingDatabases()
+  registry.ensureDefaultDatabase()
+  return newServerWithRegistry(config, registry)
 
 # ----------------------------------------------------------------------
 # Wire Protocol Helpers
@@ -230,7 +246,7 @@ proc executeQuery(db: LSMTree, ctx: ExecutionContext, query: string, params: seq
       for row in res.rows:
         var wireRow: seq[WireValue] = @[]
         for i, col in res.columns:
-          let val = if col in row: row[col] else: "\\N"
+          let val = if col in row: valueToString(row[col]) else: "\\N"
           let cType = if i < colTypes.len: colTypes[i] else: ""
           wireRow.add(valueToWire(val, cType))
         qr.rows.add(wireRow)
@@ -312,16 +328,17 @@ proc slowQueryLog(logPath: string, query: string, durationMs: int, clientId: int
     f.write(line)
   except IOError: discard
 
-proc verifyToken(secret, tokenStr: string): (bool, string, string) =
+proc verifyToken(secret, tokenStr: string): (bool, string, string, string) =
   try:
     let token = tokenStr.toJWT()
     if not token.verify(secret, HS256):
-      return (false, "", "")
+      return (false, "", "", "")
     let userId = token.claims["sub"].node.str
     let role = if "role" in token.claims: token.claims["role"].node.str else: "user"
-    return (true, userId, role)
+    let database = if "database" in token.claims: token.claims["database"].node.str else: ""
+    return (true, userId, role, database)
   except ValueError, KeyError:
-    return (false, "", "")
+    return (false, "", "", "")
 
 proc recvWithTimeout(client: AsyncSocket, size: int, timeoutMs: int): Future[string] {.async.} =
   if timeoutMs <= 0:
@@ -475,7 +492,7 @@ proc handleClient(server: Server, client: AsyncSocket, clientId: int) {.async.}
       case header.kind
       of mkAuth:
         let tokenStr = parseAuthMessage(stringToBytes(payload))
-        let (valid, userId, role) = verifyToken(secret, tokenStr)
+        let (valid, userId, role, jwtDatabase) = verifyToken(secret, tokenStr)
         if valid:
           authenticated = true
           connCtx.currentUser = userId
@@ -483,6 +500,24 @@ proc handleClient(server: Server, client: AsyncSocket, clientId: int) {.async.}
           let okMsg = makeAuthOkMessage(header.requestId)
           await client.send(bytesToString(okMsg))
           info("Client " & $clientId & " authenticated as " & userId)
+          # Switch to database from JWT claim if provided
+          if jwtDatabase.len > 0 and server.registry != nil and isValidDbName(jwtDatabase):
+            let info = getDatabaseInfo(server.registry, jwtDatabase)
+            if info != nil:
+              let targetCtx = cast[ExecutionContext](cast[pointer](info.ctx))
+              connCtx.db = info.db
+              connCtx.tables = targetCtx.tables
+              connCtx.btrees = targetCtx.btrees
+              connCtx.views = targetCtx.views
+              connCtx.ftsIndexes = targetCtx.ftsIndexes
+              connCtx.vectorIndexes = targetCtx.vectorIndexes
+              connCtx.users = targetCtx.users
+              connCtx.policies = targetCtx.policies
+              connCtx.graphs = targetCtx.graphs
+              connCtx.autoIncCounters = targetCtx.autoIncCounters
+              connCtx.sequences = targetCtx.sequences
+              connCtx.currentDatabase = jwtDatabase
+              incrementConnections(server.registry, jwtDatabase)
         else:
           let err = makeErrorMessage(header.requestId, 403, "Invalid token")
           await client.send(bytesToString(err))
@@ -510,7 +545,7 @@ proc handleClient(server: Server, client: AsyncSocket, clientId: int) {.async.}
 
         if shardCheck:
           let startTicks = getMonoTime().ticks()
-          let (success, result, errorMsg) = executeQuery(server.db, connCtx, queryStr, replication=server.replicationManager)
+          let (success, result, errorMsg) = executeQuery(connCtx.db, connCtx, queryStr, replication=server.replicationManager)
           let durationMs = int((getMonoTime().ticks() - startTicks) div 1_000_000)
 
           if durationMs >= slowThreshold:
@@ -530,7 +565,7 @@ proc handleClient(server: Server, client: AsyncSocket, clientId: int) {.async.}
         info("[" & $clientId & "] QueryParams: " & queryStr & " (" & $params.len & " params)")
 
         let startTicks = getMonoTime().ticks()
-        let (success, result, errorMsg) = executeQuery(server.db, connCtx, queryStr, params, replication=server.replicationManager)
+        let (success, result, errorMsg) = executeQuery(connCtx.db, connCtx, queryStr, params, replication=server.replicationManager)
         let durationMs = int((getMonoTime().ticks() - startTicks) div 1_000_000)
 
         if durationMs >= slowThreshold:
@@ -562,6 +597,9 @@ proc handleClient(server: Server, client: AsyncSocket, clientId: int) {.async.}
   except Exception as e:
     errorMsg("Client " & $clientId & " error: " & e.msg)
   finally:
+    # Decrement database connection counter
+    if server.registry != nil and connCtx.currentDatabase.len > 0:
+      decrementConnections(server.registry, connCtx.currentDatabase)
     acquire(server.activeConnectionsLock)
     try:
       if server.activeConnections > 0:
@@ -629,4 +667,7 @@ proc stop*(server: Server) =
   server.running = false
   if server.gossipProtocol != nil:
     server.gossipProtocol.stop()
-  server.db.close()
+  if server.registry != nil:
+    server.registry.closeAll()
+  else:
+    server.db.close()

src/barabadb/core/types.nim

@@ -1,6 +1,7 @@
 import std/times
 import std/oids
 import std/monotimes
+import std/strutils
 
 type
   ValueKind* = enum
@@ -124,3 +125,60 @@ proc newRecordId*(): RecordId =
 
 proc `==`*(a, b: RecordId): bool {.borrow.}
 proc `$`*(r: RecordId): string = $uint64(r)
+
+proc `==`*(a, b: Value): bool {.noSideEffect.} =
+  if a.kind != b.kind: return false
+  case a.kind
+  of vkNull: return true
+  of vkBool: return a.boolVal == b.boolVal
+  of vkInt8: return a.int8Val == b.int8Val
+  of vkInt16: return a.int16Val == b.int16Val
+  of vkInt32: return a.int32Val == b.int32Val
+  of vkInt64: return a.int64Val == b.int64Val
+  of vkFloat32: return a.float32Val == b.float32Val
+  of vkFloat64: return a.float64Val == b.float64Val
+  of vkString: return a.strVal == b.strVal
+  of vkBytes: return a.bytesVal == b.bytesVal
+  of vkUuid: return a.uuidVal == b.uuidVal
+  of vkDateTime: return false  # DateTime comparison not supported without side effects
+  of vkJson: return a.jsonVal == b.jsonVal
+  of vkArray: return false  # Recursive comparison not supported
+  of vkObject: return false  # Recursive comparison not supported
+  of vkVector: return a.vecVal == b.vecVal
+
+proc `!=`*(a, b: Value): bool {.noSideEffect.} =
+  return not (a == b)
+
+proc `$`*(v: Value): string =
+  case v.kind
+  of vkNull: return "\\N"
+  of vkBool: return $v.boolVal
+  of vkInt8: return $v.int8Val
+  of vkInt16: return $v.int16Val
+  of vkInt32: return $v.int32Val
+  of vkInt64: return $v.int64Val
+  of vkFloat32: return $v.float32Val
+  of vkFloat64: return $v.float64Val
+  of vkString: return v.strVal
+  of vkBytes: return "<bytes>"
+  of vkUuid: return $v.uuidVal
+  of vkDateTime: return $v.dtVal
+  of vkJson: return v.jsonVal
+  of vkArray: return $v.arrayVal
+  of vkObject: return $v.objVal
+  of vkVector: return $v.vecVal
+
+proc `==`*(a: Value, b: string): bool =
+  if a.kind == vkString: return a.strVal == b
+  if a.kind == vkNull: return b == "\\N"
+  return $a == b
+
+proc `==`*(a: string, b: Value): bool =
+  return b == a
+
+proc `in`*(v: Value, s: seq[string]): bool =
+  return $v in s
+
+proc `in`*(s: string, v: Value): bool =
+  if v.kind == vkString: return v.strVal.contains(s)
+  return ($v).contains(s)

src/barabadb/query/ast.nim

@@ -43,6 +43,10 @@ type
     nkSetVar
     nkCreateGraph
     nkDropGraph
+    nkCreateDatabase
+    nkDropDatabase
+    nkUseDatabase
+    nkShowDatabases
 
     # Clauses
     nkFrom
@@ -336,6 +340,16 @@ type
     of nkDropGraph:
       dgName*: string
       dgIfExists*: bool
+    of nkCreateDatabase:
+      cdDbName*: string
+      cdIfNotExists*: bool
+    of nkDropDatabase:
+      ddDbName*: string
+      ddIfExists*: bool
+    of nkUseDatabase:
+      udDbName*: string
+    of nkShowDatabases:
+      discard
     of nkApplyMigration:
       amName*: string
     of nkMigrationStatus:

src/barabadb/query/lexer.nim

@@ -160,6 +160,10 @@ type
     tkBfs
     tkDfs
     tkPath
+    tkDatabase
+    tkDatabases
+    tkUse
+    tkShow
 
     tkAutoIncrement
     tkSequence
@@ -382,6 +386,10 @@ const keywords*: Table[string, TokenKind] = {
   "bfs": tkBfs,
   "dfs": tkDfs,
   "path": tkPath,
+  "database": tkDatabase,
+  "databases": tkDatabases,
+  "use": tkUse,
+  "show": tkShow,
   "over": tkOver,
   "partition": tkPartition,
   "row": tkRow,

src/barabadb/query/parser.nim

@@ -1646,6 +1646,42 @@ proc parseDropGraph(p: var Parser): Node =
   result = Node(kind: nkDropGraph, dgName: name, dgIfExists: ifExists,
                 line: tok.line, col: tok.col)
 
+proc parseCreateDatabase(p: var Parser): Node =
+  let tok = p.expect(tkCreate)
+  discard p.expect(tkDatabase)
+  var ifNotExists = false
+  if p.peek().kind == tkIf:
+    discard p.advance()
+    discard p.expect(tkNot)
+    discard p.expect(tkExists)
+    ifNotExists = true
+  let name = p.expect(tkIdent).value
+  result = Node(kind: nkCreateDatabase, cdDbName: name, cdIfNotExists: ifNotExists,
+                line: tok.line, col: tok.col)
+
+proc parseDropDatabase(p: var Parser): Node =
+  let tok = p.expect(tkDrop)
+  discard p.expect(tkDatabase)
+  var ifExists = false
+  if p.peek().kind == tkIf:
+    discard p.advance()
+    discard p.expect(tkExists)
+    ifExists = true
+  let name = p.expect(tkIdent).value
+  result = Node(kind: nkDropDatabase, ddDbName: name, ddIfExists: ifExists,
+                line: tok.line, col: tok.col)
+
+proc parseUseDatabase(p: var Parser): Node =
+  let tok = p.expect(tkUse)
+  let name = p.expect(tkIdent).value
+  result = Node(kind: nkUseDatabase, udDbName: name,
+                line: tok.line, col: tok.col)
+
+proc parseShowDatabases(p: var Parser): Node =
+  let tok = p.expect(tkShow)
+  discard p.expect(tkDatabases)
+  result = Node(kind: nkShowDatabases, line: tok.line, col: tok.col)
+
 proc parseStatement*(p: var Parser): Node =
   case p.peek().kind
   of tkWith, tkSelect: p.parseSelect()
@@ -1674,6 +1710,8 @@ proc parseStatement*(p: var Parser): Node =
         p.parseCreatePolicy()
       elif next.kind == tkGraph:
         p.parseCreateGraph()
+      elif next.kind == tkDatabase:
+        p.parseCreateDatabase()
       else:
         p.parseCreateType()
     else:
@@ -1695,6 +1733,8 @@ proc parseStatement*(p: var Parser): Node =
         p.parseDropPolicy()
       elif next.kind == tkGraph:
         p.parseDropGraph()
+      elif next.kind == tkDatabase:
+        p.parseDropDatabase()
       else:
         let tok = p.advance()
         Node(kind: nkNullLit, line: tok.line, col: tok.col)
@@ -1713,6 +1753,14 @@ proc parseStatement*(p: var Parser): Node =
     p.parseRevoke()
   of tkSet:
     p.parseSetVar()
+  of tkUse:
+    p.parseUseDatabase()
+  of tkShow:
+    if p.pos + 1 < p.tokens.len and p.tokens[p.pos + 1].kind == tkDatabases:
+      p.parseShowDatabases()
+    else:
+      let tok = p.advance()
+      Node(kind: nkNullLit, line: tok.line, col: tok.col)
   of tkApply:
     if p.pos + 1 < p.tokens.len and p.tokens[p.pos + 1].kind == tkMigration:
       p.parseApplyMigration()

src/baradadb.nim

@@ -17,9 +17,11 @@ import barabadb/protocol/ssl
 import barabadb/storage/lsm
 import barabadb/storage/compaction
 import barabadb/core/raft
+import barabadb/query/executor
 import barabadb/core/gossip
 import barabadb/core/replication
 import barabadb/core/disttxn
+import barabadb/core/registry
 import barabadb/tools/repair
 import barabadb/tools/migrate
 
@@ -28,6 +30,10 @@ type
     db*: LSMTree
     strategy*: compaction.CompactionStrategy
 
+  MultiCompactionManager = ref object
+    registry: DatabaseRegistry
+    strategies: Table[string, compaction.CompactionStrategy]
+
 proc newCompactionManager*(db: LSMTree): CompactionManager =
   result = CompactionManager(db: db, strategy: compaction.newCompactionStrategy(db.dir))
   for sst in db.sstables:
@@ -88,6 +94,95 @@ proc startCompactionLoop*(cm: CompactionManager, intervalMs: int = 60000) {.asyn
     await sleepAsync(intervalMs)
     cm.compact()
 
+proc newMultiCompactionManager*(registry: DatabaseRegistry): MultiCompactionManager =
+  result = MultiCompactionManager(registry: registry, strategies: initTable[string, compaction.CompactionStrategy]())
+
+  # Initialize strategies for each existing database
+  for name in listDatabases(registry):
+    let info = getDatabaseInfo(registry, name)
+    if info != nil:
+      result.strategies[name] = compaction.newCompactionStrategy(info.db.dir)
+      for sst in info.db.sstables:
+        let meta = compaction.SSTableMeta(
+          path: sst.path, level: sst.level, minKey: sst.minKey, maxKey: sst.maxKey,
+          entryCount: sst.entryCount, sizeBytes: sst.entryCount * 64, createdAt: 0)
+        result.strategies[name].addTable(meta)
+
+proc compactAll(mcm: MultiCompactionManager) =
+  for name in listDatabases(mcm.registry):
+    let info = getDatabaseInfo(mcm.registry, name)
+    if info == nil: continue
+    let db = info.db
+
+    # Initialize strategy if not already
+    if name notin mcm.strategies:
+      mcm.strategies[name] = compaction.newCompactionStrategy(db.dir)
+      for sst in db.sstables:
+        let meta = compaction.SSTableMeta(
+          path: sst.path, level: sst.level, minKey: sst.minKey, maxKey: sst.maxKey,
+          entryCount: sst.entryCount, sizeBytes: sst.entryCount * 64, createdAt: 0)
+        mcm.strategies[name].addTable(meta)
+
+    let strategy = mcm.strategies[name]
+    acquire(db.lock)
+    try:
+      for level in 0 ..< compaction.MaxLevel:
+        if strategy.needsCompaction(level):
+          let result = strategy.compact(level)
+          if result.outputTables.len == 0: continue
+
+          var newSSTables: seq[SSTable] = @[]
+          var removedPaths = initTable[string, bool]()
+          for t in result.inputTables:
+            removedPaths[t.path] = true
+          for sst in db.sstables:
+            if sst.path notin removedPaths:
+              newSSTables.add(sst)
+
+          for meta in result.outputTables:
+            try:
+              var sst = loadSSTable(meta.path)
+              let sstName = splitFile(meta.path).name
+              sst.id = try: parseInt(sstName) except: db.nextSSTableId
+              sst.level = meta.level
+              newSSTables.add(sst)
+              db.nextSSTableId = max(db.nextSSTableId, sst.id + 1)
+            except CatchableError as e:
+              warn("Compaction output SSTable failed to load: " & meta.path & " - " & e.msg)
+
+          newSSTables.sort(proc(a, b: SSTable): int = cmp(a.id, b.id))
+          db.sstables = newSSTables
+          inc db.manifestSequence
+          try:
+            writeManifest(db)
+          except CatchableError as e:
+            warn("Failed to write MANIFEST after compaction: " & e.msg)
+    finally:
+      release(db.lock)
+
+proc startMultiCompactionLoop*(mcm: MultiCompactionManager, intervalMs: int = 60000) {.async.} =
+  while true:
+    await sleepAsync(intervalMs)
+    mcm.compactAll()
+
+proc migrateLegacyData(registry: DatabaseRegistry, config: BaraConfig) =
+  let legacyDir = config.dataDir / "server"
+  let defaultDir = registry.dataRoot / "default"
+  if dirExists(legacyDir / "sstables") and not dirExists(defaultDir):
+    info("Migrating legacy data from " & legacyDir & " to " & defaultDir)
+    createDir(defaultDir / "sstables")
+    createDir(defaultDir / "wal")
+    for kind, path in walkDir(legacyDir / "sstables"):
+      if kind == pcFile:
+        copyFile(path, defaultDir / "sstables" / splitPath(path).tail)
+    for kind, path in walkDir(legacyDir / "wal"):
+      if kind == pcFile:
+        copyFile(path, defaultDir / "wal" / splitPath(path).tail)
+    if fileExists(legacyDir / "MANIFEST"):
+      copyFile(legacyDir / "MANIFEST", defaultDir / "MANIFEST")
+    moveDir(legacyDir, legacyDir & ".migrated")
+    info("Legacy data migration complete. Original renamed to " & legacyDir & ".migrated")
+
 proc runTcpServer(config: BaraConfig) {.async.} =
   info("BaraDB TCP listening on " & config.address & ":" & $config.port)
   var server = newServer(config)
@@ -230,34 +325,45 @@ proc main() =
         warn("Failed to generate self-signed certificate. TLS disabled.")
         config.tlsEnabled = false
 
-  # Shared LSMTree instance for both TCP and HTTP servers
-  let dataDir = config.dataDir / "server"
-  let sharedDb = newLSMTree(dataDir)
+  # Create database registry with multi-database support
+  let registry = newDatabaseRegistry    (config)
+  registry.setContextFactory(proc(db: LSMTree, reg: DatabaseRegistry): ContextRef {.closure.} =
+    cast[ContextRef](cast[pointer](newExecutionContext(db, reg))))
+
+  # Migrate legacy data from old single-DB layout
+  migrateLegacyData(registry, config)
+
+  # Load existing databases and ensure default
+  registry.loadExistingDatabases()
+  registry.ensureDefaultDatabase()
+
+  info("Databases loaded: " & $listDatabases(registry).join(", "))
 
   # Start HTTP server (blocking, multi-threaded via hunos) in background thread
-  var httpServer = newHttpServerWithDb(config, sharedDb)
+  var httpServer = newHttpServerWithRegistry(config, registry)
   spawn httpServer.run(config.port + 440)  # HTTP port = TCP port + 440
 
-  # Start background compaction loop
-  let cm = newCompactionManager(sharedDb)
-  asyncCheck cm.startCompactionLoop()
+  # Start background compaction loop for all databases
+  let mcm = newMultiCompactionManager(registry)
+  asyncCheck mcm.startMultiCompactionLoop()
 
   # Create TCP server (initialization is synchronous, run is async)
   let localId {.used.} = if config.raftNodeId.len > 0: config.raftNodeId else: "node-" & $config.port
-  var tcpServer = newServerWithDb(config, sharedDb)
+  var tcpServer = newServerWithRegistry(config, registry)
 
   # Start Raft cluster if enabled
   if config.raftEnabled:
     info("Starting Raft node " & config.raftNodeId & " on port " & $config.raftPort)
     var raftNode = newRaftNode(config.raftNodeId, config.raftPeers, config.raftPort)
-    # Wire state machine to apply committed entries to the database
+    # Wire state machine to apply committed entries to the default database
+    let defaultDbInfo = getDatabaseInfo(registry, "default")
     raftNode.applyCommand = proc(cmd: string, data: seq[byte]) {.gcsafe.} =
       if cmd == "put":
         let parts = cast[string](data).split("\x00")
         if parts.len >= 2:
-          sharedDb.put(parts[0], cast[seq[byte]](parts[1]))
+          defaultDbInfo.db.put(parts[0], cast[seq[byte]](parts[1]))
       elif cmd == "delete":
-        sharedDb.delete(cast[string](data))
+        defaultDbInfo.db.delete(cast[string](data))
 
     # Wire RAFT ↔ DistTxn
     wireRaftDistTxn(raftNode, tcpServer)
@@ -291,6 +397,7 @@ proc main() =
 
   # Shutdown
   httpServer.stop()
+  tcpServer.stop()
   if tcpServer.gossipProtocol != nil:
     tcpServer.gossipProtocol.stop()