-- ============================================================
-- 002_create_knowledge_base.sql
--
-- Knowledge base for RAG (Retrieval-Augmented Generation).
-- Stores chunked text from soil science books (Albrecht et al.)
-- plus their vector embeddings from Ollama nomic-embed-text.
--
-- Run once:
--   mysql -u <user> -p cropmonitor < database/migrations/002_create_knowledge_base.sql
-- ============================================================

CREATE TABLE IF NOT EXISTS `knowledge_chunks` (
  `id`          INT UNSIGNED   NOT NULL AUTO_INCREMENT,
  `source`      VARCHAR(255)   NOT NULL COMMENT 'Book title or filename',
  `author`      VARCHAR(255)   NOT NULL DEFAULT '' COMMENT 'Author name',
  `page`        SMALLINT       NOT NULL DEFAULT 0 COMMENT 'Source PDF page number',
  `chunk_index` SMALLINT       NOT NULL DEFAULT 0 COMMENT 'Chunk position within the source',
  `chunk_text`  TEXT           NOT NULL COMMENT 'Raw text of this chunk',
  `embedding`   JSON           NOT NULL COMMENT 'Float array from nomic-embed-text (768 dims)',
  `created_at`  DATETIME       NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  FULLTEXT KEY `ft_chunk_text` (`chunk_text`),
  KEY `idx_source` (`source`(100))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;