Adding data from tables

Merging tables

Merging two existing plain tables can be more efficient than indexing the data from scratch and desired in some cases (such as merging ‘main’ and ‘delta’ tables instead of simply rebuilding ‘main’ in the ‘main+delta’ partitioning scheme). So indexer has an option to do that. Merging tables is normally faster than rebuilding, but still not instant on huge tables. Basically, it will need to read the contents of the both tables once and write the result once. Merging 100 GB and 1 GB table, for example, will result in 202 GB of I/O (but that’s still likely less than the indexing from scratch requires).

The basic command syntax is as follows:

sudo -u manticore indexer --merge DSTINDEX SRCINDEX [--rotate] [--drop-src]

Unless --drop-src is specified only the DSTINDEX table will be affected: the contents of SRCINDEX will be merged into it.

--rotate switch will be required if DSTINDEX is already being served by searchd.

The typical usage pattern is to merge a smaller update from SRCINDEX into DSTINDEX. Thus, when merging attributes the values from SRCINDEX will win if duplicate document IDs are encountered. Note, however, that the “old” keywords will not be automatically removed in such cases. For example, if there’s a keyword “old” associated with document 123 in DSTINDEX, and a keyword “new” associated with it in SRCINDEX, document 123 will be found by both keywords after the merge. You can supply an explicit condition to remove documents from DSTINDEX to mitigate that; the relevant switch is --merge-dst-range:

sudo -u manticore indexer --merge main delta --merge-dst-range deleted 0 0

This switch lets you apply filters to the destination table along with merging. There can be several filters; all of their conditions must be met in order to include the document in the resulting merged table. In the example above, the filter passes only those records where ‘deleted’ is 0, eliminating all records that were flagged as deleted.

--drop-src allows dropping SRCINDEX after the merge and before rotating the tables, which is important in case you specify DSTINDEX in killlist_target of DSTINDEX, otherwise when rotating the tables the documents that have been merged into DSTINDEX may be suppressed by SRCINDEX.

Killlist in plain tables

When using plain tables there is a problem generated by the need of having the data in the table as fresh as possible.

In this case one or more secondary (also know as delta) tables are used to capture the modified data between the time the main table was created and and current time. The modified data can mean new, updated or deleted documents. The search becomes a search over the main table and the delta table. This works with no obstacle when you just add new documents to the delta table, but when it comes to updated or deleted documents there remains the following issue.

If a document is present in both main and delta tables it can cause issues at searching as the engine will see two versions of a document and won’t know how to pick the right one. So the delta needs to tell somehow to the search that there are deleted documents in the main table that should be forgotten. Here comes kill lists.

Table kill-list

Table can maintain a list of document ids that can be used to suppress records in other tables. This feature is available for plain tables using database sources or plain tables using XML sources. In case of database sources, the source needs to provide an additional query defined by sql_query_killlist. It will store in the table a list of documents that can be used by the server to remove documents from other plain tables.

This query is expected to return a number of 1-column rows, each containing just the document ID.

In many cases the query is a union between a query that gets a list of updated documents and a list of deleted documents, e.g.:

sql_query_killlist = \
    SELECT id FROM documents WHERE updated_ts>=@last_reindex UNION \
    SELECT id FROM documents_deleted WHERE deleted_ts>=@last_reindex

Removing documents in a plain table

A plain table can contain a directive called killlist_target that will tell the server it can provide a list of document ids that should be removed from certain existing tables. The table can use either it’s document ids as the source for this list or provide a separate list.

killlist_target

Sets the table(s) that the kill-list will be applied to. Optional, default value is empty.

When you use plain tables you often need to maintain not a single table, but a set of them to be able to add/update/delete new documents sooner (read about delta table updates). In order to suppress matches in the previous (main) table that were updated or deleted in the next (delta) table you need to:

1. Create a kill-list in the delta table using sql_query_killlist
2. Specify main table as killlist_target in delta table settings:

• CONFIG

CONFIG

table products {
  killlist_target = main:kl
  path = products
  source = src_base
}

When killlist_target is specified, kill-list is applied to all the tables listed in it on searchd startup. If any of the tables from killlist_target are rotated, kill-list is reapplied to these tables. When kill-list is applied, tables that were affected save these changes to disk.

killlist_target has 3 modes of operation:

1. killlist_target = main:kl. Document ids from the kill-list of the delta table are suppressed in the main table (see sql_query_killlist).
2. killlist_target = main:id. All document ids from delta table are suppressed in the main table. Kill-list is ignored.
3. killlist_target = main. Both document ids from delta table and its kill-list are suppressed in the main table.

Multiple targets can be specified separated by comma like

killlist_target = table_one:kl,table_two:kl

You can change killlist_target settings for a table without rebuilding it by using ALTER.

But since the ‘old’ main table has already written the changes to disk, the documents that were deleted in it will remain deleted even if it is no longer in the killlist_target of the delta table.

• SQL
• HTTP

SQL HTTP

ALTER TABLE delta KILLLIST_TARGET='new_main_table:kl'

POST /cli -d "
ALTER TABLE delta KILLLIST_TARGET='new_main_table:kl'"