frostfs-node/pkg/policy/doc.go
Evgenii Stratonikov 001a23eb31 [] Support SQL-like queries for placement
JSON format is rather verbose an inconvenient to be
edited by hand. This commit implements SQL-like
language for representing placement policy.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
2020-10-02 11:25:35 +03:00

20 lines
861 B
Go

// Package policy provides facilities for creating policy from SQL-like language.
// eBNF grammar is provided in `grammar.ebnf` for illustration.
//
// Current limitations:
// 1. Grouping filter expressions in parenthesis is not supported right now.
// Requiring this will make query too verbose, making it optional makes
// our grammar not LL(1). This can be supported in future.
// 2. Filters must be defined before they are used.
// This requirement may be relaxed in future.
//
// Example query:
// REP 1 in SPB
// REP 2 in Americas
// CBF 4
// SELECT 1 Node IN City FROM SPBSSD AS SPB
// SELECT 2 Node IN SAME City FROM Americas AS Americas
// FILTER SSD EQ true AS IsSSD
// FILTER @IsSSD AND Country eq "RU" AND City eq "St.Petersburg" AS SPBSSD
// FILTER 'Continent' == 'North America' OR Continent == 'South America' AS Americas
package policy