-- fix_pages_search_vector_trigger.sql
--
-- Caps the text that feeds the full-text index of the `pages` table.
--
-- Problem:
--   PostgreSQL hard-limits a single tsvector value to 1,048,575 bytes
--   (not configurable). The trigger function
--   pages_search_vector_update() built the vector from the full
--   content column, so pages with very large text content (observed:
--   ~2 MB, e.g. pkg.go.dev "?tab=importedby" pages) aborted the whole
--   INSERT with ProgramLimitExceeded ("string is too long for
--   tsvector") and crashed all crawler workers.
--
-- Fix:
--   Feed at most the first 200,000 characters of the content into
--   to_tsvector(). Even at worst-case 4 bytes per UTF-8 character this
--   stays far below the tsvector limit. The full text remains stored
--   in the content column - only the search index is truncated.
--   200,000 characters cover the meaningful prose of essentially all
--   real pages; the oversized ones are link lists with no index value.
--
-- Run once on the jonassearch database as its owner, e.g.:
--   psql -h 127.0.0.1 -p 25432 -U jonassearch -d jonassearch \
--       -f fix_pages_search_vector_trigger.sql
--
-- Safe to run repeatedly (CREATE OR REPLACE) and safe to run while the
-- crawler is running: existing rows keep their vectors, only newly
-- INSERTed/UPDATEd rows use the capped version.

CREATE OR REPLACE FUNCTION pages_search_vector_update()
RETURNS trigger AS $$
BEGIN
    -- Cap the indexed text: a tsvector value may hold at most
    -- 1,048,575 bytes. left(content, 200000) can never exceed that
    -- (200000 chars * max 4 bytes UTF-8 = 800,000 bytes).
    NEW.search_vector :=
        to_tsvector('simple', left(coalesce(NEW.content, ''), 200000));
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- Notes for the DBA:
-- * If your existing function uses a different text search config
--   (e.g. 'german' or 'english') or indexes additional columns
--   (title, headings), port the left(..., 200000) cap into YOUR
--   function body instead of blindly replacing it - check first with:
--     SELECT prosrc FROM pg_proc WHERE proname =
--         'pages_search_vector_update';
-- * The trigger itself (CREATE TRIGGER pages_search_vector_update
--   BEFORE INSERT OR UPDATE ...) is unchanged; only the function body
--   above is replaced.
-- * Optional backfill of already-stored rows (this runs UPDATEs over
--   the whole table; run during low traffic):
--     UPDATE pages SET content = content
--       WHERE search_vector IS NULL
--          OR octet_length(search_vector::text) > 1048575;