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DBA Management

# Introduction to DB Administration

This part of SqlUtil contain some additional tools to handle subset of database administration. Common application developer usually does not need to handle anything described in this section on his own.

Warning
  Database administration is complex task and it requires knowledge in various areas of IT. Always ask your DBA if and when you can use these tools.

DBA tools are part of the AbstractDatabase (or Database) classes. Methods described below are wrappers around database specific commands.

# Index Management

- SqlUtil::AbstractDatabase::rebuildIndex()

Index rebuilding is quite controversial task and it is highly variable for each database server. And even worse - it's varying between database server versions too. Modern database servers usually do not need to rebuild indexes in regular operations, but there can be situations when it's required still. Like: testing DB features, index corruption as a result of HW failure, storage parameters changing etc.

The easiest criteria which can be quickly and easily given to you is it not to rebuild or coalesce any index unless you have a specific, proven reason for doing so.

rebuildIndex() methods always takes a index name or an SqlUtil::AbstractIndex instance as first argument. The second argument is an optional hash with rebuild index options. These options are specific for each database server. See driver-specific modules for more info.

new Database(ds).rebuildIndex("ix_foo_bar");

## Oracle Options

Oracle backend implementation uses `ALTER` `INDEX` `REBUILD` statement internally.

Option | Type | Description
`parallel` | Boolean | Use parallel keyword in the statement if it's set to True
`logging` | Boolean | Use `logging` keyword in the statement if it's set to True. By default `nologging` keyword is used.
`statistics` | Boolean | Use `compute` `statistics` keyword in the stetement if it's set to True
`tablespace` | String | Rebuild index in given tablespace
`cond_rebuild` | Boolean | Rebuild index only when it meets `INDEX_STATS` criteria
`cond_maxheight` | Integer | maximum index height before rebuilding index
`cond_maxleafpct` | Integer | maximum percentage of deleted leaf nodes before rebuilding index

## PostgreSQL Options

PostgreSQL uses `REINDEX` `INDEX` statement internally.

There are no special options for PostgreSQL.

## MySQL Options

MySQL does not offer any command to rebuild an index. Exception `MYSQL-REBUILD-INDEX-ERROR` is thrown if is the rebuildIndex method called for MySQL.

Use reclaimSpace method for MySQL.

# Database Statistics

- SqlUtil::AbstractDatabase::computeStatistics()

Database statistics are critical metadata used by SQL optimizers to build as good execution plans as possible. Some DB environments refresh statistics on regular basis, some not. All is usually highly configured by DBA.

The optional argument holds options for statistics. These options are specific for each database server. See driver-specific modules for more info.

## Oracle Options

Oracle uses `DBMS_STATS` package internally. With `GATHER_SCHEMA_STATS` or `GATHER_TABLE_STATS` depending on options set below.

Statistics are calculated in currently logged user's schema.

Please consult Oracle documentation for exact option meanings.

Option | Type | Description
`tables` | list of strings | If it's set, the table by table statistics are computed with `GATHER_TABLE_STATS`. Otherwise the full schema with `GATHER_SCHEMA_STATS` is used.
`estimate_percent` | Integer | A percent as integer given. `DBMS_STATS.AUTO_SAMPLE_SIZE` is used as a default
`block_sample` | Boolean | Whether use random block sampling
`method_opt` | String | an optional size clause. By default "for all columns size auto" is used.
`degree` | Integer | a degree of parallelism. Default is NULL.
`granularity` | String | granularity of statistics to collect. Default is "ALL"
`cascade` | Boolean | True = gather statistics on indexes as well, False = do not make statistics for indexes. By default "dbms_stats.auto_cascade" is used.
`stattab` | String | user statistics table identifier describing where to save the current statistics
`statid` | String | identifier to associate with these statistics within `stattab`
`options` | String | further specification of which objects to gather statistics. By default "gather auto"
`statown` | String | schema containing `stattab` (if different than `ownname`)

Example: Compute statistics for enumerated tables only.

hash<auto> opts = (
"tables": ("workflows", "workflow_instance"),
);
db.computeStatistics(opts);

## PostgreSQL Options

PostgreSQL uses `ANALYZE` `TABLE` internally.

Option | Type | Description
`tables` | list of strings | If it's set, the table by table statistics are computed. Otherwise all tables in the user DB are used.

## MySQL Options

MySQL uses `ANALYZE` `TABLE` internally.

Please consult MySQL documentation for exact option meanings.

Option | Type | Description
`tables` | list of strings | If it's set, the table by table statistics are computed. Otherwise all tables in the user DB are used.
`no-binlog` | Boolean | If True, the "no_write_to_binlog" is used. If False (default), the "local" keyword is used.

# Space Management

- SqlUtil::AbstractDatabase::reclaimSpace()

Space reclaiming can be done if there was a huge deletion from some tables. As usual causes are DB-dependent.

The optional argument holds options for space management. These options are specific for each database server. See driver-specific modules for more info.

## Oracle Options

Oracle uses `ALTER` `TABLE` `SHRINK` `SPACE` `CASCADE` statement internally. So it requires enabled row movement.

Please consult Oracle documentation for more information.

Option | Type | Description
`tables` | list of strings | If it's set, the table by table statistics are computed. Otherwise all tables in the user DB are used.

## PostgreSQL Options

PostgreSQL uses `VACUUM` internally.

Please consult PostgreSQL documentation for exact option meanings.

Option | Type | Description
`tables` | list of strings | If it's set, the table by table statistics are computed. Otherwise all tables in the user DB are used.
`full` | Boolean | True if `full` keyword should be used
`analyze` | Boolean | True if `analyze` keyword should be used

## MySQL Options

MySQL uses `OPTIMIZE` `TABLE` internally.

Please consult MySQL documentation for exact option meanings.

Option | Type | Description
`tables` | list of strings | If it's set, the table by table statistics are computed. Otherwise all tables in the user DB are used.
`no-binlog` | Boolean | If True, the "no_write_to_binlog" is used. If False (default), the "local" keyword is used.