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pixa/internal/db/migrations/001_schema.sql
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sneak 03b11e9703
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Declare only the tables and columns pixa writes and reads (closes #310)
Removes output_content and request_cache, which nothing writes, and every
column that was written but never read: the host, path, query, content_type
and fetched_at of source_content, the content_type and created_at of
variant_content, and the status_code, error_message and fetched_at of
negative_cache.

StoreSource no longer takes the fetch result and LookupSource returns only
the source key. StoreVariant no longer takes a content type and
StoreNegative no longer takes a status code or message, so
extractStatusCode and the status constants, which only fed status_code,
are gone. Reconciliation adopts a variant file without opening it, as its
row no longer records a content type. Tests that set or checked a removed
column follow.

Model: opus-5-5
2026-10-21 16:32:49 +00:00

130 lines
4.7 KiB
SQL

-- Migration 001: Initial schema
-- Creates all tables for the pixa caching image proxy
-- Source images, one row per source URL
-- Files stored at: cache/sources/<ab>/<cd>/<source_key>, where source_key
-- is the SHA-256 of the source's host, path and query
CREATE TABLE IF NOT EXISTS source_content (
source_key TEXT PRIMARY KEY,
size_bytes INTEGER NOT NULL,
last_accessed_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
);
CREATE INDEX IF NOT EXISTS idx_source_content_last_accessed
ON source_content(last_accessed_at);
-- Processed variant blobs
-- Files stored at: cache/variants/<ab>/<cd>/<cache_key>. Tracked here
-- (like source content blobs above) so total cache usage is known
-- without a directory scan, and so LRU eviction has a timestamp to order
-- on. A cache hit does not read this table: it takes the content type
-- from the file's first bytes, and its last_accessed_at is written
-- later, in a batch.
CREATE TABLE IF NOT EXISTS variant_content (
cache_key TEXT PRIMARY KEY,
size_bytes INTEGER NOT NULL,
last_accessed_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
);
CREATE INDEX IF NOT EXISTS idx_variant_content_last_accessed
ON variant_content(last_accessed_at);
-- Total cache usage: the sum of size_bytes over source_content and
-- variant_content, kept by the triggers below in the same statement
-- that adds, removes or resizes a row, so eviction reads this one row
-- instead of summing both tables. Each trigger also adds one to
-- change_count; the reconciliation pass, which sums both tables a page
-- at a time, corrects total_size_bytes only if change_count did not
-- move while it summed.
CREATE TABLE IF NOT EXISTS cache_usage (
id INTEGER PRIMARY KEY CHECK (id = 1),
total_size_bytes INTEGER NOT NULL DEFAULT 0,
change_count INTEGER NOT NULL DEFAULT 0
);
INSERT OR IGNORE INTO cache_usage (id) VALUES (1);
CREATE TRIGGER IF NOT EXISTS source_content_usage_insert
AFTER INSERT ON source_content
BEGIN
UPDATE cache_usage
SET total_size_bytes = total_size_bytes + NEW.size_bytes,
change_count = change_count + 1
WHERE id = 1;
END;
CREATE TRIGGER IF NOT EXISTS source_content_usage_delete
AFTER DELETE ON source_content
BEGIN
UPDATE cache_usage
SET total_size_bytes = total_size_bytes - OLD.size_bytes,
change_count = change_count + 1
WHERE id = 1;
END;
CREATE TRIGGER IF NOT EXISTS source_content_usage_update
AFTER UPDATE OF size_bytes ON source_content
BEGIN
UPDATE cache_usage
SET total_size_bytes = total_size_bytes - OLD.size_bytes + NEW.size_bytes,
change_count = change_count + 1
WHERE id = 1;
END;
CREATE TRIGGER IF NOT EXISTS variant_content_usage_insert
AFTER INSERT ON variant_content
BEGIN
UPDATE cache_usage
SET total_size_bytes = total_size_bytes + NEW.size_bytes,
change_count = change_count + 1
WHERE id = 1;
END;
CREATE TRIGGER IF NOT EXISTS variant_content_usage_delete
AFTER DELETE ON variant_content
BEGIN
UPDATE cache_usage
SET total_size_bytes = total_size_bytes - OLD.size_bytes,
change_count = change_count + 1
WHERE id = 1;
END;
CREATE TRIGGER IF NOT EXISTS variant_content_usage_update
AFTER UPDATE OF size_bytes ON variant_content
BEGIN
UPDATE cache_usage
SET total_size_bytes = total_size_bytes - OLD.size_bytes + NEW.size_bytes,
change_count = change_count + 1
WHERE id = 1;
END;
-- Negative cache: source URLs whose fetch failed with an upstream error
-- status, or whose first bytes did not match their Content-Type. pixa does
-- not fetch such a URL again until its row expires.
CREATE TABLE IF NOT EXISTS negative_cache (
id INTEGER PRIMARY KEY AUTOINCREMENT,
source_host TEXT NOT NULL,
source_path TEXT NOT NULL,
source_query TEXT NOT NULL DEFAULT '',
expires_at DATETIME NOT NULL,
UNIQUE(source_host, source_path, source_query)
);
CREATE INDEX IF NOT EXISTS idx_negative_cache_expires ON negative_cache(expires_at);
-- Cache statistics for monitoring
CREATE TABLE IF NOT EXISTS cache_stats (
id INTEGER PRIMARY KEY CHECK (id = 1),
hit_count INTEGER NOT NULL DEFAULT 0,
miss_count INTEGER NOT NULL DEFAULT 0,
upstream_fetch_count INTEGER NOT NULL DEFAULT 0,
upstream_fetch_bytes INTEGER NOT NULL DEFAULT 0,
transform_count INTEGER NOT NULL DEFAULT 0,
last_updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);
INSERT OR IGNORE INTO cache_stats (id) VALUES (1);
-- A random value that a login session carries from its login. pixa makes it
-- when the table has no row, and each logout replaces it; a login session
-- carrying another value is refused, so logging out ends every login session.
CREATE TABLE IF NOT EXISTS logout (
id INTEGER PRIMARY KEY CHECK (id = 1),
logout_value TEXT NOT NULL
);