Truncate Table

Data Manipulation

Synopsis

Clears every value and presence bit on the named virtual table, keeping it allocated for further $<table>.Field writes.

Schema

- truncate_table:
    name: <string>
    description: <text>
    if: <script>
    tag: <string>
    disabled: <boolean>
    ignore_failure: <boolean>
    on_failure: <processor[]>
    on_success: <processor[]>

Configuration

Field	Required	Default	Description
name	Y		Table to clear. Must be one of the 12 registered tables (see Create Table), matched case-insensitively. Supports templating, e.g. name: "{{table}}".
description	N		Explanatory note.
if	N		Condition that must be true for the processor to run.
tag	N		Identifier for this processor instance.
disabled	N	false	When true, the processor is skipped.
ignore_failure	N	false	Continue pipeline processing if the processor fails.
on_failure	N		See Handling Failures.
on_success	N		See Handling Success.

Details

What Gets Cleared

truncate_table resets every column of the named table to absent — clearing both its stored value and its presence bit, not just setting fields back to a zero value like "" or 0. A $<table>.Field == nil check reads true for every column immediately after truncation, exactly as it would on a freshly create_table-d table. The table's backing struct stays allocated, so subsequent $<table>.Field writes need no new create_table call.

If the truncated table is the entry's current output table (selected by Use Table), it stays selected — truncation only clears the struct's contents, it never changes which table use_table picked. The entry keeps marshaling from the same, now empty, table.

Failure Mode

Truncating a table that was never create_table-d on this entry is a no-op, not a failure — the table's member is already absent, so there is nothing to clear. Truncating a name that is not one of the 12 registered tables at all still fails the processor with unknown virtual table: "<name>", same as create_table and drop_table. Add ignore_failure: true to treat that as a soft skip.

Examples

Clearing a Table's Contents

Writing a field, then truncating before selecting the table as output...	{} - create_table: name: Syslog - set: field: $syslog.SyslogMessage value: "first line" - truncate_table: name: Syslog - use_table: name: Syslog
SyslogMessage is cleared back to absent, so the marshaled table carries no fields at all...	{}

The Table Stays Allocated for Further Writes

Truncating, then writing a new value into the same table without calling create_table again...	{} - create_table: name: Syslog - set: field: $syslog.SyslogMessage value: "first line" - truncate_table: name: Syslog - set: field: $syslog.SyslogMessage value: "second line" - use_table: name: Syslog
The write succeeds immediately — truncate_table only clears contents, it never deallocates the table...	{ "SyslogMessage": "second line" }

No-Op on a Table That Was Never Created

Truncating Syslog before anything has ever create_table-d it...	{ "message": "untouched" } - truncate_table: name: Syslog
No error is raised — an uncreated table has nothing to clear, and the event passes through unmodified...	{ "message": "untouched" }

Failing on an Unknown Table Name

Naming a table that isn't one of the 12 registered schemas...	{} - truncate_table: name: Frobnicate ignore_failure: true
Frobnicate isn't a registered table, so — unlike an uncreated but known table — this fails; ignore_failure skips the failure...	{}