Function

Hologres use PostgreSQL 11 semantics but only support a subset of all the functions supported by PostgreSQL. Below tables list all functions Hologres supported currently. For detailed information please refer to PostgreSQL document.

Mathematcial Functions

Function	Supported	Added by Hologres
abs(bigint)	Yes	No
abs(int)	Yes	No
abs(float8)	Yes	No
abs(float4)	Yes	No
abs(numeric)	Yes	No
cbrt(dp)	Yes	No
ceil(dp )	Yes	No
ceil(numeric)	Yes	No
ceiling(dp )	Yes	No
ceiling(numeric)	Yes	No
degrees(dp)	Yes	No
exp(dp)	Yes	No
exp(numeric)	Yes	No
floor(dp )	Yes	No
floor(numeric)	Yes	No
ln(dp)	Yes	No
ln(numeric)	Yes	No
log(dp)	Yes	No
log(numeric)	Yes	No
log(b numeric, x numeric)	Yes	No
mod(bigint, x)	Yes	No
mod(int, x)	Yes	No
pi()	Yes	No
power(a dp, b dp)	Yes	No
power(a numeric, b numeric)	Yes	No
radians(dp)	Yes	No
round(dp )	Yes	No
round(numeric)	Yes	No
round(v numeric, s int)	Yes	No
sign(dp )	Yes	No
sign(numeric)	Yes	No
sqrt(dp)	Yes	No
sqrt(numeric)	Yes	No
trunc(dp)	Yes	No
trunc(numeric)	Yes	No
trunc(v numeric, s int)	Yes	No
width_bucket(operand numeric, b1 numeric, ...)	Yes	No
random()	Yes	No

Trigonometric Functions

Function	Supported	Added by Hologress
acos(bigint)	Yes	No
acos(int)	Yes	No
acos(float8)	Yes	No
acos(float4)	Yes	No
acos(numeric)	Yes	No
asin(bigint)	Yes	No
asin(int)	Yes	No
asin(float8)	Yes	No
asin(float4)	Yes	No
asin(numeric)	Yes	No
atan(bigint)	Yes	No
atan(int)	Yes	No
atan(float8)	Yes	No
atan(float4)	Yes	No
atan(numeric)	Yes	No
atan2(bigint)	Yes	No
atan2(int)	Yes	No
atan2(float8)	Yes	No
atan2(float4)	Yes	No
atan2(numeric)	Yes	No
cos(bigint)	Yes	No
cos(int)	Yes	No
cos(float8)	Yes	No
cos(float4)	Yes	No
cos(numeric)	Yes	No
cot(bigint)	Yes	No
cot(int)	Yes	No
cot(float8)	Yes	No
cot(float4)	Yes	No
cot(numeric)	Yes	No
sin(bigint)	Yes	No
sin(int)	Yes	No
sin(float8)	Yes	No
sin(float4)	Yes	No
sin(numeric)	Yes	No
tan(bigint)	Yes	No
tan(int)	Yes	No
tan(float8)	Yes	No
tan(float4)	Yes	No
tan(numeric)	Yes	No

String Functions and Operators

Function	Supported	Added by Hologress
string		string
bit_length(string)	Yes	No
char_length(string)	Yes	No
lower(string)	Yes	No
octet_length(string)	Yes	No
position(substring in string)	Yes	No
substring(string [from int] [for int])	Yes	No
substring(string from pattern)	Yes	No
substring(string from pattern for escape)	Yes	No
trim([leading	trailing	both] [characters] from string)
trim([lea	tra	both] [from] string [, char] )
upper(string)	Yes	No

Other Postgres String Functions

Function	Supported	Added by Hologress
ascii(string)	Yes	No
btrim(string text [, characters text])	Yes	No
chr(int)	Yes	No
concat(str "any" [, str "any" [, ...] ])	Yes	No
initcap(string)	Yes	No
length(string)	Yes	No
lpad(string text, length int [, fill text])	Yes	No
ltrim(string text [, characters text])	Yes	No
md5(string)	Yes	No
parse_ident(quali_iden text [,...] )	Yes	No
quote_ident(string text)	Yes	No
quote_literal(string text)	Yes	No
regexp_matches(string text, pattern text )	Yes	No
regexp_replace(str text, pat text, replace text )	Yes	No
regexp_split_to_array(string text, pattern text )	Yes	No
regexp_split_to_table(string text, pattern text )	Yes	No
repeat(string text, number int)	Yes	No
replace(string text, from text, to text)	Yes	No
rpad(string text, length int [, fill text])	Yes	No
rtrim(string text [, characters text])	Yes	No
strpos(string, substring)	Yes	No
substr(string, from [, count])	Yes	No
starts_with(string, prefix)	Yes	No
to_hex(number int or bigint)	Yes	No
translate(string text, from text, to text)	Yes	No

Pattern Matching

Function	Supported	Added by Hologress
like	Yes	No
not like	Yes	No
similar to	Yes	No
not similar to	Yes	No
rlike ~	Yes	No
rlike !~*	Yes	No
rlike ~*	Yes	No
rlike !~	Yes	No
substring()	Yes	No
regexp_replace()	Yes	No
regexp_split_to_table	Yes	No
regexp_split_to_array	Yes	No

Date/Time Formating Functions

Function	Supported	Added by Hologress
to_char(timestamp, text)	Yes	No
to_char(int, text)	Yes	No
to_char(double precision, text)	Yes	No
to_date(text, text)	Yes	No
to_number(text, text)	Yes	No
to_timestamp(text, text)	Yes	No
date - date	Yes	No
clock_timestamp()	Yes	No
current_date	Yes	No
current_timestamp	Yes	No
date_part(text, timestamp)	Yes	No
date_trunc(text, timestamp)	Yes	No
extract(field from timestamp)	Yes	No
isfinite(date)	Yes	No
isfinite(timestamp)	Yes	No
isfinite(interval)	Yes	No
make_date(year int, month int, day int)	Yes	No
localtimestamp	Yes	No
now()	Yes	No
statement_timestamp()	Yes	No
timeofday()	Yes	No
transaction_timestamp()	Yes	No
to_timestamp(double precision)	Yes	No

Conditional Expressions

Function	Supported	Added by Hologress
case	Yes	No
coalesce	Yes	No
nullif	Yes	No
greatest	Yes	No
least	Yes	No

Array Functions

Function	Supported	Added by Hologress
array_append(anyarray, anyelement)	Yes	No
array_dims(anyarray)	Yes	No
array_lower(anyarray, int)	Yes	No
array_prepend(anyelement, anyarray)	Yes	No
array_upper(anyarray, int)	Yes	No
unnest(anyarray)	Yes	No

General-Purpose Aggregate Functions

Function	Supported	Added by Hologress
array_agg(bigint)	Yes	No
array_agg(bool)	Yes	No
array_agg(text)	Yes	No
array_agg(float8)	Yes	No
array_agg(float4)	Yes	No
array_agg(int)	Yes	No
avg(bigint)	Yes	No
avg(float8)	Yes	No
avg(float4)	Yes	No
avg(int)	Yes	No
bit_and(bigint)	Yes	No
bit_and(int)	Yes	No
bit_or(bigint)	Yes	No
bit_or(int)	Yes	No
bool_and(bool)	Yes	No
bool_or(bool)	Yes	No
cout(*)	Yes	No
cout(bigint)	Yes	No
cout(numeric)	Yes	No
every(bool)	Yes	No
max(bigint)	Yes	No
max(float8)	Yes	No
max(float4)	Yes	No
max(int)	Yes	No
max(numeric)	Yes	No
min(bigint)	Yes	No
min(float8)	Yes	No
min(float4)	Yes	No
min(int)	Yes	No
min(numeric)	Yes	No
sum(bigint)	Yes	No
sum(float8)	Yes	No
sum(float4)	Yes	No
sum(int)	Yes	No
sum(numeric)	Yes	No
string_agg(expression, delimiter)	Yes	No
corr(Y, X)	Yes	No
covar_pop(Y, X)	Yes	No
covar_samp(Y, X)	Yes	No
regr_avgx(Y, X)	Yes	No
regr_avgy(Y, X)	Yes	No
regr_count(Y, X)	Yes	No
regr_intercept(Y, X)	Yes	No
regr_r2(Y, X)	Yes	No
regr_slope(Y, X)	Yes	No
regr_sxx(Y, X)	Yes	No
regr_sxy(Y, X)	Yes	No
regr_syy(Y, X)	Yes	No
stddev(int)	Yes	No
stddev(numeric)	Yes	No
stddev(float8)	Yes	No
stddev_pop(int)	Yes	No
stddev_pop(numeric)	Yes	No
stddev_pop(float8)	Yes	No
stddev_samp(int)	Yes	No
stddev_samp(numeric)	Yes	No
stddev_samp(float8)	Yes	No
variance(int)	Yes	No
variance(numeric)	Yes	No
var_pop(float8)	Yes	No
var_pop(int)	Yes	No
var_pop(numeric)	Yes	No
var_samp(float8)	Yes	No
var_samp(int)	Yes	No
var_samp(numeric)	Yes	No

Ordered-Set Aggregate Functions

Function	Supported	Added by Hologress
GROUPING(args...)	Yes	Yes

Window Functions

Function	Supported	Added by Hologress
row_number()	Yes	No
rank()	Yes	No
dense_rank()	Yes	No
percent_rank()	Yes	No
lag()	Yes	No
lead()	Yes	No
first_value()	Yes	No
last_value()	Yes	No

Subquery Expressions

Function	Supported	Added by Hologress
EXISTS (subquery)	Yes	No
IN (subquery)	Yes	No
NOT IN (subquery)	Yes	No
ANY (subquery)	Yes	No
SOME (subquery)	Yes	No

Row and Array Comparisons

Function	Supported	Added by Hologress
NOT IN (values,...)	Yes	No
IN (values,...)	Yes	No

Set Returning functions

Function	Supported	Added by Hologress
generate_series(start, stop)	Yes	No
generate_series(start, stop, step)	Yes	No
generate_series(start, stop, step interval)	Yes	No
generate_subscripts(array anyarray, dim int)	Yes	No

Session Information Functions

Function	Supported	Added by Hologress
current_catalog	Yes	No
current_database()	Yes	No
current_query()	Yes	No
current_role	Yes	No
current_schema[()]	Yes	No
current_schemas(boolean)	Yes	No
current_user	Yes	No
inet_client_addr()	Yes	No
inet_client_port()	Yes	No
inet_server_addr()	Yes	No
inet_server_port()	Yes	No
pg_backend_pid()	Yes	No
pg_blocking_pids(int)	Yes	No
session_user	Yes	No
user	Yes	No
version()	Yes	No
current_setting(setting_name)	Yes	No

Access Privilege Inquiry Functions

Function	Supported	Added by Hologress
has_any_column_privilege(user, table, privilege)	Yes	No
has_any_column_privilege(table, privilege)	Yes	No
has_column_privilege(user, table, column, privilege)	Yes	No
has_column_privilege(table, column, privilege)	Yes	No
has_database_privilege(user, database, privilege)	Yes	No
has_database_privilege(database, privilege)	Yes	No
has_foreign_data_wrapper_privilege(user, fdw, privilege)	Yes	No
has_foreign_data_wrapper_privilege(fdw, privilege)	Yes	No
has_function_privilege(user, function, privilege)	Yes	No
has_function_privilege(function, privilege)	Yes	No
has_language_privilege(user, language, privilege)	Yes	No
has_language_privilege(language, privilege)	Yes	No
has_schema_privilege(user, schema, privilege)	Yes	No
has_schema_privilege(schema, privilege)	Yes	No
has_server_privilege(user, server, privilege)	Yes	No
has_server_privilege(server, privilege)	Yes	No
has_table_privilege(user, table, privilege)	Yes	No
has_table_privilege(table, privilege)	Yes	No
has_tablespace_privilege(user, tablespace, privilege)	Yes	No
has_tablespace_privilege(tablespace, privilege)	Yes	No
has_type_privilege(user, type, privilege)	Yes	No
has_type_privilege(type, privilege)	Yes	No
pg_has_role(user, role, privilege)	Yes	No
pg_has_role(role, privilege)	Yes	No

Public API Functions

Standard PostgreSQL functions cannot meet all business requirements, so Hologres added some new functions as public API which can be used to simplify development process. Next chapter will describe public API functions in detail.