BEGIN;

CREATE TABLE words (
--  name         type      constraints
    id           BIGSERIAL PRIMARY KEY,
    language_id  BIGINT    NOT NULL REFERENCES languages (id),
    primary_form VARCHAR   NOT NULL,

--  CONSTRAINT name                      CHECK (condition)
    CONSTRAINT primary_form_is_sane_text CHECK (is_sane_text(primary_form))
);

CREATE TABLE word_forms (
--  name    type      constraints
    id      BIGSERIAL PRIMARY KEY,
    word_id BIGINT    NOT NULL REFERENCES words (id),
    value   VARCHAR   NOT NULL,

--  CONSTRAINT name               CHECK (condition)
    CONSTRAINT value_is_sane_text CHECK (is_sane_text(value))
);

CREATE TABLE word_form_example_texts (
    id              BIGSERIAL PRIMARY KEY,
    word_form_id    BIGINT    NOT NULL REFERENCES word_forms (id),
    example_text_id BIGINT    NOT NULL REFERENCES example_texts (id)
);

CREATE UNIQUE INDEX word_forms_word_value_index ON word_forms (word_id, value);

COMMIT;