API Reference

While the Guide and README provide a more narrative-based approach to covering this extension’s functionality, users can consult this document when something more like a reference is needed.

Basic Functionality, Tables and Views

These functions are for creating and managing time-series tables

enable_ts_table

Designates an existing table as a time-series table and creates an initial set of partitions.

Arguments

  • target_table_id (regclass), required — an existing table to enhance with time-series functionality
  • partition_duration (interval), default 7 days — the duration of time covered by a single partition
  • partition_lead_time (interval), default 1 mon — how far in advance (from now) to make future partitions
  • initial_table_start (timestamptz), default NULL — the timestamp of the earliest partition to create. If NULL, four partitions (before now) will be created by default

Considerations

target_table_id must point to a table that has been declaratively partitioned using PostgreSQL’s partitioning features. It must be partitioned on a time-like column (date, timestamp, timestamptz) which has a NOT NULL constraint.

If any of the above prerequisites are not met, error messages will guide the user toward correcting the problems.

Returns

void. If any problems are encountered, an error will be raised.

set_ts_lead_time

Modifies “lead time” for new partition creation for a table.

Arguments

  • target_table_id (regclass), required — a time-series enhanced table
  • new_lead_time (interval), required — a new lead time for the time-series table

Returns

interval. The previous lead time for this table.

ts_config

This table contains information about time-series tables.

Columns

  • table_id (regclass, NOT NULL) — a table with time-series enhancements
  • partition_duration (interval, NOT NULL) — the width of partitions within this table
  • partition_lead_time (interval, NOT NULL) — how far in advance to create partitions for this table
  • retention_duration (interval) — how far back to retain partitions. If NULL, keep partitions forever
  • compression_duration (interval) — how far back to keep partitions uncompressed. After this point, they will have their storage changed to columnar. If NULL, compression is never automatically applied

ts_table_info

Provides usage information about time-series tables

Columns

  • table_id (regclass) — a table with time-series enhancements
  • table_size_bytes (numeric) — data size for the table
  • index_size_bytes (numeric) — index size for the table
  • total_size_bytes (numeric) — total size for the table

ts_part_info

Provides usage information about individual time-series partitions

Columns

  • table_id (regclass) — a table with time-series enhancements
  • part_id (regclass) — a partition of a time-series table
  • part_range (text) — the time range covered by this partition
  • table_size_bytes (bigint) — data size for the partition
  • index_size_bytes (bigint) — index size for the partition
  • total_size_bytes (bigint) — total size for the partition
  • access_method (name) — access method used by the partition (e.g. heap or columnar)

Retention

set_ts_retention_policy

Sets the retention policy for a time-series table. Lazily applied on an hourly schedule.

Arguments

  • target_table_id (regclass), required — the time-series enhanced table whose retention schedule is to be modified
  • new_retention (interval), required — the new retention duration for the time-series table

Returns

interval, the previous policy for this table, or NULL if none was set.

clear_ts_retention_policy

Clears the retention policy for a table (so its data will never be dropped).

Arguments

  • target_table_id (regclass), required — the time-series enhanced table whose retention schedule is to be cleared

Returns

interval, the previous policy for this table, or NULL if none was set.

Compression

set_ts_compression_policy

Sets the compression policy for a time-series table. Lazily applied on an hourly schedule.

Arguments

  • target_table_id (regclass), required — the time-series enhanced table whose compression schedule is to be modified
  • new_compression (interval), required — the new compression duration for the time-series table

Returns

interval, the previous policy for this table, or NULL if none was set.

clear_ts_compression_policy

Clears the compression policy for a table (so its data will never be dropped).

Arguments

  • target_table_id (regclass), required — the time-series enhanced table whose compression schedule is to be cleared

Returns

interval, the previous policy for this table, or NULL if none was set.

Analytics Functions

These functions are not related to the maintenance of time-series tables, but do sometimes rely on the related metadata to function. They are intended to make time-series queries easier to read and maintain.

first/last

These aggregates return a column’s value in the first or last row as sorted by a different column. For instance, first(name, birthdate) would return the name of the person with the first birthday in a set.

Most often used with a GROUP BY clause.

Arguments

  • value (any type), required — the column (or expression) whose value should be returned
  • rank (any type), required — the column (or expression) to be used to sort the input rows

Returns

type of value. In short, the aggregate finds the lowest (first) or highest (last) row in the input rows and returns the value expression from that row.

date_bin_table

This set-returning function (table function) wraps a time-series table in order to bin all time values to a specified stride. For instance, by asking for 1 hour bins, all time data will be aligned to the hour.

Bins for which the source table has no data will still be emitted, but with NULL in every non-time column. To limit how many such rows are returned, an explicit range argument is used. Furthermore, the bin alignment will begin at the start point of this range.

Arguments

  • target_table_elem (any table type), required — an element cast to the type of the target table. Idiomatically written as NULL::target_table, this helps PostgreSQL determine the shape of output rows. target_table must be a table with time-series enhancements
  • time_stride (interval), required — the “stride” or width of the output bins, e.g. '1 day', '15 minutes’, etc.
  • time_range (tstzrange), required — the desired range of data to return. Date bins are aligned to the start of this range

Returns

SETOF target_table_elem%TYPE. In other words, the output of this function may be treated as a table with the same schema as its first argument. Rows are not aggregated: only binning and NULL imputation are performed. A common use of this function is to treat it like a table and place it in the FROM clause of a query before performing other aggregation.

locf

Last-Observation-Carried-Forward. This is a window function that operates over time-series data, replacing any missing data with the most recently seen non-NULL value.

Arguments

  • value (any type), required — input to the window function

Returns

value if value is not NULL

The most recent non-NULL value if value is NULL