got rid of the hot/cold blob, all blobs are "cold" now

src/becca/entities/abstract_becca_entity.js

@@ -119,23 +119,10 @@ class AbstractBeccaEntity {
         return this;
     }
 
-    /**
-     * Hot entities keep stable blobId which is continuously updated and is not shared with other entities.
-     * Cold entities can still update its blob, but the blobId will change (and new blob will be created).
-     * Functionally this is the same, it's an optimization to avoid creating a new blob every second with auto saved
-     * text notes.
-     *
-     * @protected
-     */
-    _isHot() {
-        return false;
-    }
-
     /** @protected */
     _setContent(content, opts = {}) {
         // client code asks to save entity even if blobId didn't change (something else was changed)
         opts.forceSave = !!opts.forceSave;
-        opts.forceCold = !!opts.forceCold;
         opts.forceFrontendReload = !!opts.forceFrontendReload;
 
         if (content === null || content === undefined) {
@@ -149,7 +136,7 @@ class AbstractBeccaEntity {
             content = Buffer.isBuffer(content) ? content : Buffer.from(content);
         }
 
-        const unencryptedContentForHashCalculation = this.getUnencryptedContentForHashCalculation(content);
+        const unencryptedContentForHashCalculation = this.#getUnencryptedContentForHashCalculation(content);
 
         if (this.isProtected) {
             if (protectedSessionService.isProtectedSessionAvailable()) {
@@ -160,16 +147,38 @@ class AbstractBeccaEntity {
         }
 
         sql.transactional(() => {
-            let newBlobId = this._saveBlob(content, unencryptedContentForHashCalculation, opts);
+            const newBlobId = this.#saveBlob(content, unencryptedContentForHashCalculation, opts);
+            const oldBlobId = this.blobId;
 
-            if (newBlobId !== this.blobId || opts.forceSave) {
+            if (newBlobId !== oldBlobId || opts.forceSave) {
                 this.blobId = newBlobId;
                 this.save();
+
+                if (newBlobId !== oldBlobId) {
+                    this.#deleteBlobIfNoteUsed(oldBlobId);
+                }
             }
         });
     }
 
-    getUnencryptedContentForHashCalculation(unencryptedContent) {
+    #deleteBlobIfNoteUsed(blobId) {
+        if (sql.getValue("SELECT 1 FROM notes WHERE blobId = ? LIMIT 1", [blobId])) {
+            return;
+        }
+
+        if (sql.getValue("SELECT 1 FROM attachments WHERE blobId = ? LIMIT 1", [blobId])) {
+            return;
+        }
+
+        if (sql.getValue("SELECT 1 FROM note_revisions WHERE blobId = ? LIMIT 1", [blobId])) {
+            return;
+        }
+
+        sql.execute("DELETE FROM blobs WHERE blobId = ?", [blobId]);
+        sql.execute("DELETE FROM entity_changes WHERE entityName = 'blobs' AND entityId = ?", [blobId]);
+    }
+
+    #getUnencryptedContentForHashCalculation(unencryptedContent) {
         if (this.isProtected) {
             // a "random" prefix make sure that the calculated hash/blobId is different for an encrypted note and decrypted
             const encryptedPrefixSuffix = "t$[nvQg7q)&_ENCRYPTED_?M:Bf&j3jr_";
@@ -181,54 +190,47 @@ class AbstractBeccaEntity {
         }
     }
 
-    /** @protected */
-    _saveBlob(content, unencryptedContentForHashCalculation, opts = {}) {
-        let newBlobId;
-        let blobNeedsInsert;
+    #saveBlob(content, unencryptedContentForHashCalculation, opts = {}) {
+        /*
+         * We're using the unencrypted blob for the hash calculation, because otherwise the random IV would
+         * cause every content blob to be unique which would balloon the database size (esp. with revisioning).
+         * This has minor security implications (it's easy to infer that given content is shared between different
+         * notes/attachments, but the trade-off comes out clearly positive).
+         */
+        const newBlobId = utils.hashedBlobId(unencryptedContentForHashCalculation);
+        const blobNeedsInsert = !sql.getValue('SELECT 1 FROM blobs WHERE blobId = ?', [newBlobId]);
 
-        if (this._isHot() && !opts.forceCold) {
-            newBlobId = this.blobId || utils.randomBlobId();
-            blobNeedsInsert = true;
-        } else {
-            /*
-             * We're using the unencrypted blob for the hash calculation, because otherwise the random IV would
-             * cause every content blob to be unique which would balloon the database size (esp. with revisioning).
-             * This has minor security implications (it's easy to infer that given content is shared between different
-             * notes/attachments, but the trade-off comes out clearly positive).
-             */
-            newBlobId = utils.hashedBlobId(unencryptedContentForHashCalculation);
-            blobNeedsInsert = !sql.getValue('SELECT 1 FROM blobs WHERE blobId = ?', [newBlobId]);
+        if (!blobNeedsInsert) {
+            return newBlobId;
         }
 
-        if (blobNeedsInsert) {
-            const pojo = {
-                blobId: newBlobId,
-                content: content,
-                dateModified: dateUtils.localNowDateTime(),
-                utcDateModified: dateUtils.utcNowDateTime()
-            };
+        const pojo = {
+            blobId: newBlobId,
+            content: content,
+            dateModified: dateUtils.localNowDateTime(),
+            utcDateModified: dateUtils.utcNowDateTime()
+        };
 
-            sql.upsert("blobs", "blobId", pojo);
+        sql.upsert("blobs", "blobId", pojo);
 
-            const hash = utils.hash(`${newBlobId}|${pojo.content.toString()}`);
+        const hash = utils.hash(`${newBlobId}|${pojo.content.toString()}`);
 
-            entityChangesService.addEntityChange({
-                entityName: 'blobs',
-                entityId: newBlobId,
-                hash: hash,
-                isErased: false,
-                utcDateChanged: pojo.utcDateModified,
-                isSynced: true,
-                // overriding componentId will cause frontend to think the change is coming from a different component
-                // and thus reload
-                componentId: opts.forceFrontendReload ? utils.randomString(10) : null
-            });
+        entityChangesService.addEntityChange({
+            entityName: 'blobs',
+            entityId: newBlobId,
+            hash: hash,
+            isErased: false,
+            utcDateChanged: pojo.utcDateModified,
+            isSynced: true,
+            // overriding componentId will cause frontend to think the change is coming from a different component
+            // and thus reload
+            componentId: opts.forceFrontendReload ? utils.randomString(10) : null
+        });
 
-            eventService.emit(eventService.ENTITY_CHANGED, {
-                entityName: 'blobs',
-                entity: this
-            });
-        }
+        eventService.emit(eventService.ENTITY_CHANGED, {
+            entityName: 'blobs',
+            entity: this
+        });
 
         return newBlobId;
     }

src/becca/entities/battachment.js

@@ -118,7 +118,6 @@ class BAttachment extends AbstractBeccaEntity {
      * @param content
      * @param {object} [opts]
      * @param {object} [opts.forceSave=false] - will also save this BAttachment entity
-     * @param {object} [opts.forceCold=false] - blob has to be saved as cold
      * @param {object} [opts.forceFrontendReload=false] - override frontend heuristics on when to reload, instruct to reload
      */
     setContent(content, opts) {

src/becca/entities/bnote.js

@@ -227,15 +227,10 @@ class BNote extends AbstractBeccaEntity {
         return JSON.parse(content);
     }
 
-    _isHot() {
-        return ['text', 'code', 'relationMap', 'canvas', 'mermaid'].includes(this.type);
-    }
-
     /**
      * @param content
      * @param {object} [opts]
      * @param {object} [opts.forceSave=false] - will also save this BNote entity
-     * @param {object} [opts.forceCold=false] - blob has to be saved as cold
      * @param {object} [opts.forceFrontendReload=false] - override frontend heuristics on when to reload, instruct to reload
      */
     setContent(content, opts) {
@@ -1610,10 +1605,7 @@ class BNote extends AbstractBeccaEntity {
 
                 const revisionAttachment = noteAttachment.copy();
                 revisionAttachment.parentId = noteRevision.noteRevisionId;
-                revisionAttachment.setContent(noteAttachment.getContent(), {
-                    forceSave: true,
-                    forceCold: true
-                });
+                revisionAttachment.setContent(noteAttachment.getContent(), { forceSave: true });
 
                 // content is rewritten to point to the revision attachments
                 noteContent = noteContent.replaceAll(`attachments/${noteAttachment.attachmentId}`, `attachments/${revisionAttachment.attachmentId}`);

src/etapi/etapi.openapi.yaml

@@ -784,7 +784,7 @@ components:
           readOnly: true
         blobId:
           type: string
-          description: ID of the blob object. For "cold" notes, this is effectively a content hash
+          description: ID of the blob object which effectively serves as a content hash
         attributes:
           $ref: '#/components/schemas/AttributeList'
           readOnly: true

src/services/notes.js

@@ -892,6 +892,8 @@ function eraseAttachments(attachmentIdsToErase) {
 }
 
 function eraseUnusedBlobs() {
+    // this method is rather defense in depth - in normal operation, the unused blobs should be erased immediately
+    // after getting unused (handled in entity._setContent())
     const unusedBlobIds = sql.getColumn(`
         SELECT blobs.blobId
         FROM blobs