1. Serial Number and Indexing in PostgreSQL
University of Tehran
ECE Department
Database Lab.

2. Serial Number Definition
CREATE TABLE Test ( id SERIAL PRIMARY KEY, name character varying (20) ) INSERT INTO Test ("name") values ('Ali'); Incorrect: INSERT INTO Test values ('Ali');

3. Serial Data Types Data Type Storage Size Range smallserial 2 bytes
bigserial
8 bytes
1 to

4. Another method for Serial Number Definition
CREATE SEQUENCE Test_id_seq; CREATE TABLE tablename ( id integer NOT NULL DEFAULT nextval(' Test_id_seq ') ); ALTER SEQUENCE Test_id_seq OWNED BY Test.id;

5. Indexing in PostgreSQL

6. CREATE TABLE test1 ( id integer, content varchar ); SELECT content FROM test1 WHERE id = 10; CREATE INDEX test1_id_index ON test1 (id);

7. Index Types PostgreSQL provides several index types:
B-tree
Hash
GiST
SP-GiST
GIN
Each index type uses a different algorithm that is best suited to different types of queries.
By default, the CREATE INDEX command creates B- tree indexes, which fit the most common situations.

8. B+Tree Usage equality and range queries < <= = >= >
BETWEEN and IN
IS NULL or IS NOT NULL
pattern matching operators LIKE and ~ if the pattern is a constant and is anchored to the beginning of the string
for example, col LIKE 'foo%' or col ~ '^foo', but not col LIKE '%bar'.
can also be used to retrieve data in sorted order. This is not always faster than a simple scan and sort, but it is often helpful.

9. Hash Usage CREATE INDEX name ON table USING hash (column);
Hash indexes can only handle simple equality comparisons.
= operator.

10. GiST Usage
not a single kind of index, but rather an infrastructure within which many different indexing strategies can be implemented.
the particular operators with which a GiST
PostgreSQL includes GiST operator classes for several two-dimensional geometric data types, which support indexed queries using these operators:
<< &< &> >> <<| &<| |&> |>> @> ~= &&

11. Example
GiST indexes are also capable of optimizing "nearest-neighbor" searches, such as
SELECT * FROM places ORDER BY location <- > point '(101,456)' LIMIT 10;
which finds the ten places closest to a given target point. The ability to do this is again dependent on the particular operator class being used.

12. SP-GiST like GiST indexes
offer an infrastructure that supports various kinds of searches.
SP-GiST permits implementation of a wide range of different non-balanced disk-based data structures, such as quadtrees, k-d trees, and radix trees (tries).
PostgreSQL includes SP-GiST operator classes for two-dimensional points:
<< >> ~= <^ >^

13. GIN
GIN indexes are inverted indexes which can handle values that contain more than one key, arrays for example.
Like GiST and SP-GiST, GIN can support many different user-defined indexing strategies and the particular operators classes for one- dimensional arrays
@> = &&

14. PostGIS Spatial Database

15. PostGIS Example
CREATE TABLE "public". "GASSTATION"("gid" SERIAL PRIMARY KEY, "gs_id" float,"name" varchar(48),"type" varchar(16) )
SELECT AddGeometryColumn('public','GASSTATION','geom',4326,'POI NT',2)
INSERT INTO "public". "GASSTATION" ( "gs_id","name","type","geom") VALUES
(' e+07', 'AmirAbaad','GAS', st_geometryfromtext('POINT ( )',4326))

16. PostGIS Example
SELECT "name", st_distance("geom", st_geometryfromtext('POINT( )',4326)) FROM "public". "GASSTATION"
SELECT * FROM "public". "GASSTATION" WHERE st_distance("geom", st_geometryfromtext('POINT( )',4326)) < 10

17. Create GiST index in PostGIS
CREATE INDEX gs_index ON "public"."GASSTATION" USING GIST (geom);
SELECT * FROM "public"."GASSTATION" WHERE _ST_Contains(geom, st_geometryfromtext('POLYGON((0 0, 0 10, , 10 0, 0 0))',4326))