Meta functions

These functions provide table information including column details and metadata. These functions are particularly useful for checking if tables contain a designated timestamp column.

table_columns

table_columns('tableName') returns the schema of a table

Arguments:

• tableName is the name of an existing table as a string

Return value:

Returns a table with the following columns:

• column - name of the available columns in the table
• type - type of the column
• indexed - if indexing is applied to this column
• indexBlockCapacity - how many row IDs to store in a single storage block on disk
• symbolCached - whether this symbol column is cached
• symbolCapacity - how many distinct values this column of symbol type is expected to have
• designated - if this is set as the designated timestamp column for this table

For more details on the meaning and use of these values, see the CREATE TABLE documentation.

Examples:

Get all columns in a table

table_columns('my_table')

column	type	indexed	indexBlockCapacity	symbolCached	symbolCapacity	designated
symb	SYMBOL	true	1048576	false	256	false
price	DOUBLE	false	0	false	0	false
ts	TIMESTAMP	false	0	false	0	true
s	STRING	false	0	false	0	false

Get designated timestamp column

SELECT column, type, designated FROM table_columns('my_table') WHERE designated

column	type	designated
ts	TIMESTAMP	true

Get the count of column types

SELECT type, count() FROM table_columns('my_table');

type	count
SYMBOL	1
DOUBLE	1
TIMESTAMP	1
STRING	1

tables

tables() returns all tables in the database including table metadata.

Arguments:

• tables() does not require arguments.

Return value:

Returns a table.

Examples:

List all tables

tables();

id	name	designatedTimestamp	partitionBy	maxUncommittedRows	o3MaxLag	walEnabled	directoryName
1	my_table	ts	DAY	500000	30000000 0	false	my_table
2	device_data	null	NONE	10000	30000000	false	device_data
3	short_lived	null	HOUR	10000	30000000	false	short_lived (->)

All tables in reverse alphabetical order

tables() ORDER BY name DESC;

id	name	designatedTimestamp	partitionBy	maxUncommittedRows	o3MaxLag	walEnabled	directoryName
2	device_data	null	NONE	10000	30000000	false	device_data
1	my_table	ts	DAY	500000	300000000	false	my_table
3	short_lived	ts	HOUR	10000	30000000	false	short_lived (->)

note

(->) means the table was created using the IN VOLUME clause.

All tables with a daily partitioning strategy

tables() WHERE partitionBy = 'DAY'

id	name	designatedTimestamp	partitionBy	maxUncommittedRows	walEnabled	directoryName
1	my_table	ts	DAY	500000	true	my_table

wal_tables

wal_tables() returns the WAL status for all WAL tables in the database.

Arguments:

• wal_tables() does not require arguments.

Return value:

Returns a table including the following information:

• name - table name
• suspended - suspended status flag
• writerTxn - the last committed transaction in TableWriter
• sequencerTxn - the last committed transaction in the sequencer

Examples:

List all tables

wal_tables();

name	suspended	writerTxn	sequencerTxn
sensor_wal	false	2	4
weather_wal	false	3	3
test_wal	true	7	9