db_ops.h File Reference

High(ish) level instructions for general database operations. More...

#include "../../diskio/include/diskio.h"
#include "../../diskio/include/db_structs.h"
#include "../../diskio/include/diskiod.h"
#include "record.h"
#include "cursor.h"
#include "cursor_bt.h"
#include <string.h>
#include <assert.h>

Include dependency graph for db_ops.h:

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Go to the source code of this file.

Macros
#define	TABLES   0
	The id, and the address of the TABLES table.
#define	COLUMNS   1
	The id, and the address of the COLUMNS table.
#define	TABLES_NAMES   2
	The address of the TABLES_NAMES table.
#define	COLUMNS_TIDX   3
	The address of the COLUMNS_NAMES table.
#define	COLUMNS_NAMES   4
	The address of the COLUMNS_NAMES table.

Functions
int	initialize_tables ()
	Create initial tables. More...
void *	get_row (Page root, Key key, Cursor **cursor)
	Get row from table with root root.
struct record *	get_n_record (Page root, Key key, size_t n)
	Retrieves the nth record from the row with key key.
Page	get_table_addr (Key table_id)
	Get the table tree address of the given table.
Key	get_table_id (char *table_name)
	Get the table id from a table name.
Key	get_next_id (Key root_id)
	Get the next available index in the table.
Key	insert_row (Key root_id, struct record **records, size_t size)
	Insert a row into the table with key root_id.
Key	advanced_insert_row (Key tidx, struct record **records, size_t size)
Page	create_table (char *table_name, char **column_names, short nb_cols)
	Creates a new table in the database. More...
short *	get_column_offsets (Key table_id, char *col_names[], size_t nb_cols)
	Get the offsets of a list of columns in a table. More...
char *	select_row_columns (char *table_name, Key key, char *col_names[], size_t nb_cols)
	Selects a row from a table with the given key. More...
char *	select_all (char *table_name, char *col_names[], size_t nb_cols)
	Selects all rows from a table. More...
char *	select_where (char *table_name, char *col_names[], size_t nb_cols, char *where_col_name, struct record *where_record)
	Selects all rows from a table where the given column is equal to the given value. More...
void	exit_db ()
	Exits and closes the database properly.

Detailed Description

High(ish) level instructions for general database operations.

Author

Jack Royer

Date

2022-05-29

Function Documentation

create_table()

Page create_table	(	char *	table_name,
		char **	column_names,
		short	nb_cols
	)

Creates a new table in the database.

Parameters

table_name	The name of the table to create.
column_names	The names of the columns in the table.
nb_cols	The number of columns in the table.

Returns

The identifier of the newly created table, -1 if an error occurred.

get_column_offsets()

short * get_column_offsets	(	Key	table_id,
		char *	col_names[],
		size_t	nb_cols
	)

Get the offsets of a list of columns in a table.

For a table TABLE with columns idx, COL 0, COL 1, COL 2; the offset of COL 2 is 2.

Use this function to get all the offsets at once as it is a costly operation.

Parameters

table_id	The identifier of the table (it can be obtained with get_table_id)
column_names	The names of the columns
nb_cols	The number of columns

Returns

The offsets of the columns in the table, NULL if an error occurred.

initialize_tables()

int initialize_tables

(

)

Create initial tables.

Creates the initial tables in the database if they are missing. There are 2 tables:

• TABLES: a table of all tables in the database.
• COLUMNS: a table of all columns in the database.

These trees have "hidden" columns: they are marked with an underscore.

TABLES table

It's root is on page TABLES, it has index TABLES.

The table has the following columns:

Column	Offset	Type	Description
_idx	-	Key	The index of the table in the database
name	0	char *	The name of the table
_root	1	Page	the root page of the table
_next_id	2	Key	the next available id for a row in the table

COLUMNS table

It's root is on page COLUMNS, it has index COLUMNS. It points to the index trees associated with each column.

The table has the following columns:

Column	Offset	Type	Description
_idx	-	Key	The index of the column in the database
table_idx	0	Key	The index of the table
name	1	char *	The name of the column
_offset	2	short	The offset of the column in the table
_root	3	Page	The root page of the index tree

select_all()

char * select_all	(	char *	table_name,
		char *	col_names[],
		size_t	nb_cols
	)

Selects all rows from a table.

Parameters

table_name	The name of the table
col_names	The names of the columns the user wants to select
nb_cols	The number of columns the user wants to select, if 0 select all

Returns

char* The result of the query, NULL if an error occured

select_row_columns()

char * select_row_columns	(	char *	table_name,
		Key	key,
		char *	col_names[],
		size_t	nb_cols
	)

Selects a row from a table with the given key.

Parameters

table_name	The name of the table to select from
key	The key of the row to select
col_names	The names of the columns the user wants to select
nb_cols	The number of columns to select

select_where()

char * select_where	(	char *	table_name,
		char *	col_names[],
		size_t	nb_cols,
		char *	where_col_name,
		struct record *	where_record
	)

Selects all rows from a table where the given column is equal to the given value.

Parameters

table_name	The name of the table
col_names	The names of the columns the user wants to select
nb_cols	The number of columns the user wants to select, if 0 select all
where_col_name	The name of the column to compare
where_record	The value to compare

Returns

char* The result of the query, NULL if an error occured