Mysql – SQL DB design to support user feeds (in application like facebook)

database-designMySQL

I have a social network server with a MySql DB. I want to show the users feeds like done in Facebook. Example – UserX now Friend with userY, userX did like on postX etc.

Currently I have table: C1 : UserId C2 : LogType (now friend, did like etc) C3 : ObjectId (Can be userId or postId) – set depending on the LogType.

Currently to get all related logs to show to the user I do the following queries: 1. Get All user Friends userIds 2. Query all rows which C1 is in userIds (I query completed) 3. Scan the DB and see – if LogType equals DidLike, check if post's OwnerId is the userId – if yes add it to logs.

And so on.

Obvious this is not efficient at all.

I am looking for a better way. I thought I had in mind: Create a new table (in addition to the Log table) C1 : UserId C2 : LogId (from Log table) C3 : UserID of the one who did the action When querying logs – look in the table and get related Logs (by LogId) from LogTable.

Updating the table: Whenever user doing action that should be in the log: 1. Add the Log entry to LogTable. 2. Scan the DB and see which users are interested with the Log (Who my friends are, Who is the owner of the post) and add related entries to the new table. (must be done in BG). 3. If user UNFRIEND another user – then loko in the logs for all rows where C3 == UNFRIENDED user id and delete them.

Any opinions? Other suggestions?

Best Answer

Get rid of ambiguous columns like object_id. Use log_type to determine what you are querying on. So something like:

CREATE TABLE logs (
    log_id bigint AUTO_INCREMENT, -- not sure if this is the mysql syntax
    user_id int references users(id),
    post_id bigint references posts(id)
);

A second point is I would suggest changing the friend/unfriend to be immediate so it doesn't hit this table. This should be only for logging actions to posts, not friendships and the like. If you must log and propagate, create a separate table for this.

Related Solutions

Mysql – Peer Review of Database Design

I think that you really need an ER diagram here. Try YED for doing the diagram. It helps you visualise things better. I'm involved in designing rdbms for critical gov operations and was taught in university to never design things in code. I feel some of your tables have too many fks and are breaking the normalisation process.

If you have an ER diagram i would love to see it. Its the way I always start. First define entities, the attributes, then do relationship matrix, then the entity relationship diagram, then do out the tables and do 1nf etc. It is an awful lot of work to start off with but when you can visualise it it starts to make sense. it means less maintainability, more accuracy, more performance and better data.

Some rows have three pks - I presume that this is a combination pk or else it has broken the rules of normalisation - only one primary key per row. You will eventually run into difficulty. Would be interested in seeing more.

The diagram you have shown looks somewhat like an ER diagram but you do not appear to have considered the attributes or relationships in it e.g. one to many, many to many.
I would be really glad to help with the design. But normalisation has been broken here. Therefore your data will let you down in the long run. A well designed database is crucial here especially since you are tracking those brilliant movies :)

Any chance I could rent one from this db :)

MySQL – Script to Automate Creation of Audit Tables and Triggers

I just wrote this earlier today. It's a select statement working off the information_schema database, which produces the schema for the audit tables and the triggers.

SET GLOBAL group_concat_max_len = 1000;

SET @dbName = "[[[your_db_name_here]]]";

SELECT concat("DROP TABLE IF EXISTS `", @dbName, "`.`", table_data.audit_table, "`;\r",
          "CREATE TABLE `", @dbName, "`.`", table_data.audit_table, "`\r",
          "(\r",
          "  `auditAction` ENUM ('INSERT', 'UPDATE', 'DELETE'),\r",
          "  `auditTimestamp` DATETIME DEFAULT CURRENT_TIMESTAMP,\r",
          "  `auditId` INT(14) AUTO_INCREMENT,",
          column_defs, ",\r"
          "  PRIMARY KEY (`auditId`),\r",
          "  INDEX (`auditTimestamp`)\r",
          ")\r",
          "  ENGINE = InnoDB;\r\r",
          "DROP TRIGGER IF EXISTS `", @dbName, "`.`", table_data.insert_trigger, "`;\r",
          "CREATE TRIGGER `", @dbName, "`.`", table_data.insert_trigger, "`\r",
          "  AFTER INSERT ON `", @dbName, "`.`", table_data.db_table, "`\r",
          "  FOR EACH ROW INSERT INTO `", @dbName, "`.`", table_data.audit_table, "`\r",
          "     (`auditAction`,", table_data.column_names, ")\r",
          "  VALUES\r",
          "     ('INSERT',", table_data.NEWcolumn_names, ");\r\r",
          "DROP TRIGGER IF EXISTS `", @dbName, "`.`", table_data.update_trigger, "`;\r",
          "CREATE TRIGGER `", @dbName, "`.`", table_data.update_trigger, "`\r",
          "  AFTER UPDATE ON `", @dbName, "`.`", table_data.db_table, "`\r",
          "  FOR EACH ROW INSERT INTO `", @dbName, "`.`", table_data.audit_table, "`\r",
          "     (`auditAction`,", table_data.column_names, ")\r",
          "  VALUES\r",
          "     ('UPDATE',", table_data.NEWcolumn_names, ");\r\r",
          "DROP TRIGGER IF EXISTS `", @dbName, "`.`", table_data.delete_trigger, "`;\r",
          "CREATE TRIGGER `", @dbName, "`.`", table_data.delete_trigger, "`\r",
          "  AFTER DELETE ON `", @dbName, "`.`", table_data.db_table, "`\r",
          "  FOR EACH ROW INSERT INTO `", @dbName, "`.`", table_data.audit_table, "`\r",
          "     (`auditAction`,", table_data.column_names, ")\r",
          "  VALUES\r",
          "     ('DELETE',", table_data.OLDcolumn_names, ");\r\r"
)
FROM (
   # This select builds a derived table of table names with ordered and grouped column information in different
   # formats as needed for audit table definitions and trigger definitions.
   SELECT
     table_order_key,
     table_name                                                                      AS db_table,
     concat("audit_", table_name)                                                    AS audit_table,
     concat(table_name, "_inserts")                                                  AS insert_trigger,
     concat(table_name, "_updates")                                                  AS update_trigger,
     concat(table_name, "_deletes")                                                  AS delete_trigger,
     group_concat("\r  `", column_name, "` ", column_type ORDER BY column_order_key) AS column_defs,
     group_concat("`", column_name, "`" ORDER BY column_order_key)                   AS column_names,
     group_concat("`NEW.", column_name, "`" ORDER BY column_order_key)               AS NEWcolumn_names,
     group_concat("`OLD.", column_name, "`" ORDER BY column_order_key)               AS OLDcolumn_names
   FROM
     (
       # This select builds a derived table of table names, column names and column types for
       # non-audit tables of the specified db, along with ordering keys for later order by.
       # The ordering must be done outside this select, as tables (including derived tables)
       # are by definition unordered.
       # We're only ordering so that the generated audit schema maintains a resemblance to the
       # main schema.
       SELECT
         information_schema.tables.table_name        AS table_name,
         information_schema.columns.column_name      AS column_name,
         information_schema.columns.column_type      AS column_type,
         information_schema.tables.create_time       AS table_order_key,
         information_schema.columns.ordinal_position AS column_order_key
       FROM information_schema.tables
         JOIN information_schema.columns
           ON information_schema.tables.table_name = information_schema.columns.table_name
       WHERE information_schema.tables.table_schema = @dbName
             AND information_schema.columns.table_schema = @dbName
             AND information_schema.tables.table_name NOT LIKE "audit\_%"
     ) table_column_ordering_info
   GROUP BY table_name
 ) table_data
ORDER BY table_order_key
INTO OUTFILE "[[[your_output_file]]]"

Best Answer

Related Solutions

Mysql – Peer Review of Database Design

MySQL – Script to Automate Creation of Audit Tables and Triggers

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