schema

schema(table|dbHandle)

table | dbHandle can be a table object or a database handle.

Display information about the schema of a table or a database. The function returns an unordered dictionary containing the following information (in alphabetical order):

• atomic: the level at which the atomicity is guaranteed for a write transaction. It can be TRANS or CHUNK.
• chunkGranularity: the chunk granularity which determines whether to allow concurrent writes to different tables in the same chunk. It can be TABLE or DATABASE.
• clusterReplicationEnabled: whether asynchronous replication has been enabled.
• colDefs: information about each column in the table:
  • name: column name
  • typeString: column type
  • typeInt: the type ID
  • comment: comment on the column
• compressMethods: the compression methods used for specified columns of a DFS table.
  • name: Column names
  • compressMethods: Compression algorithm applied, including "lz4", "delta", or "zstd".
• databaseDir: the directory where the database is stored.
• databaseOwner: the database creator.
• partitionColumnIndex: the index that indicates the positions of partitioning columns. It returns -1 for a dimension table.
• partitionColumnName: the partitioning column names.
• partitionColumnType: the data type ID (which can be checked at Data Types and Data Forms) of the partitioning column.
• partitionSchema: how the partitions are organized
• partitionSites (optional): If the parameter locations is specified for function database, it displays the ip:port information of the specified node.
• partitionTypeName / partitionType: the partitioning scheme and the corresponding ID, including VALUE(1), RANGE(2), LIST(3), COMPO(4), HASH(5).
• tableComment: the comment for DFS tables.
• tableOwner: the table creator.

OLAP database:

n=1000000
ID=rand(10, n)
x=rand(1.0, n)
t=table(ID, x)
db=database("dfs://rangedb101", RANGE, 0 5 10)
pt = db.createPartitionedTable(t, `pt, `ID)
pt.append!(t)
pt=loadTable(db,`pt);

schema(db);
// output
databaseDir->dfs://rangedb101
partitionSchema->[0,5,10]
partitionSites->
atomic->TRANS
chunkGranularity->TABLE
partitionType->2
partitionTypeName->RANGE
partitionColumnType->4
clusterReplicationEnabled->1
databaseOwner->admin

OLAP table:

schema(pt);
// output
chunkGranularity->TABLE
tableOwner->admin
compressMethods->
name compressMethods
---- ---------------
ID   lz4            
x    lz4            

colDefs->
name typeString typeInt comment
---- ---------- ------- -------
ID   INT        4              
x    DOUBLE     16             

chunkPath->
partitionColumnIndex->0
partitionColumnName->ID
partitionColumnType->4
partitionType->2
partitionTypeName->RANGE
partitionSchema->[0,5,10]
partitionSites->