pydeephaven.query#

class Query(session, table)[source]#

Bases: TableInterface

A Query object is used to define and execute a sequence of Deephaven table operations on the server.

When the query is executed, the table operations specified for the Query object are batched together and sent to the server in a single request, thus avoiding multiple round trips between the client and the server. The result of executing the query is a new Deephaven table.

Note, an application should always use the factory method on the Session object to create a Query instance as the constructor is subject to future changes to support more advanced features already planned.

agg_by(agg, by)[source]#

Add a Combined Aggregation operation to the query.

Parameters:

by (List[str]) – the group-by column names
agg (ComboAggregation) – the combined aggregation definition

Returns:

self

aj(table, on, joins=[], match_rule=MatchRule.LESS_THAN_EQUAL)[source]#

Add a as-of join operation to the query.

Parameters:

table (Table) – the right-table of the join
on (List[str]) – the columns to match, can be a common name or an equal expression, i.e. “col_a = col_b” for different column names
joins (List[str], optional) – a list of the columns to be added from the right table to the result table, can be renaming expressions, i.e. “new_col = col”; default is empty
match_rule (MatchRule, optional) – the match rule for the as-of join, default is LESS_THAN_EQUAL

Returns:

self

avg_by(by=[])[source]#

Add an avg-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names, default is empty
Returns:: self

count(col)[source]#

Add a count operation to the query.

Parameters:: col (str) – the name of the column whose values to be counted
Returns:: self

count_by(col, by=[])[source]#

Add a count-by aggregation to the query.

Parameters:

col (str) – the name of the column to store the counts
by (List[str], optional) – the group-by column names, default is empty

Returns:

self

drop_columns(cols)[source]#

Add a drop-columns operation to the query.

Parameters:: cols (List[str]) – the list of column names
Returns:: self

exact_join(table, on, joins=[])[source]#

Add an exact-join operation to the query.

Parameters:

table (Table) – the right-table of the join
on (List[str]) – the columns to match, can be a common name or an equal expression, i.e. “col_a = col_b” for different column names
joins (List[str], optional) – a list of the columns to be added from the right table to the result table, can be renaming expressions, i.e. “new_col = col”; default is empty

Returns:

self

exec()[source]#

Execute the query on the server and return the result table.

Returns:: a Table object
Raises:: DHError –

first_by(by=[])[source]#

Add a first-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names, default is empty
Returns:: self

group_by(by=[])[source]#

Add a group-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names; default is empty
Returns:: self

head(num_rows)[source]#

Add a head operation to the query.

Parameters:: num_rows (int) – the number of rows at the head of table
Returns:: self

head_by(num_rows, by)[source]#

Add a head-by operation to the query.

Parameters:

num_rows (int) – the number of rows at the beginning of each group
by (List[str]) – the group-by column names

Returns:

self

join(table, on=[], joins=[], reserve_bits=10)[source]#

Add a cross-join operation to the query.

Parameters:

table (Table) – the right-table of the join
on (List[str]) – the columns to match, can be a common name or an equal expression, i.e. “col_a = col_b” for different column names
joins (List[str], optional) – a list of the columns to be added from the right table to the result table, can be renaming expressions, i.e. “new_col = col”; default is empty
reserve_bits (int, optional) – the number of bits of key-space to initially reserve per group; default is 10

Returns:

self

last_by(by=[])[source]#

Add a last-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names, default is empty
Returns:: self

lazy_update(formulas)[source]#

Add an lazy-update operation to the query.

Parameters:: formulas (List[str]) – the column formulas
Returns:: self

max_by(by=[])[source]#

Add a max-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names, default is empty
Returns:: self

median_by(by=[])[source]#

Add a median-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names, default is empty
Returns:: self

min_by(by=[])[source]#

Add a min-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names, default is empty
Returns:: self

natural_join(table, on, joins=[])[source]#

Add a natural-join operation to the query.

Parameters:

table (Table) – the right-table of the join
on (List[str]) – the columns to match, can be a common name or an equal expression, i.e. “col_a = col_b” for different column names
joins (List[str], optional) – a list of the columns to be added from the right table to the result table, can be renaming expressions, i.e. “new_col = col”; default is empty

Returns:

self

raj(table, on, joins=[], match_rule=MatchRule.GREATER_THAN_EQUAL)[source]#

Add a reverse as-of join operation to the query.

Parameters:

table (Table) – the right-table of the join
on (List[str]) – the columns to match, can be a common name or an equal expression, i.e. “col_a = col_b” for different column names
joins (List[str], optional) – a list of the columns to be added from the right table to the result table, can be renaming expressions, i.e. “new_col = col”; default is empty
match_rule (MatchRule, optional) – the match rule for the as-of join, default is GREATER_THAN_EQUAL

Returns:

self

select(formulas=[])[source]#

Add a select operation to the query.

Parameters:: formulas (List[str], optional) – the column formulas, default is empty
Returns:: self

select_distinct(cols=[])[source]#

Add a select-distinct operation to the query.

Parameters:: cols (List[str], optional) – the list of column names, default is empty
Returns:: self

snapshot()[source]#

Add a snapshot operation to the query.

Returns:: self

snapshot_when(trigger_table, stamp_cols=None, initial=False, incremental=False, history=False)[source]#

Add a snapshot_when operation to the query.

Returns:: self

sort(order_by, order=[])[source]#

Add sort operation to the query.

Parameters:

order_by (List[str]) – the names of the columns to be sorted on
order (List[SortDirection], optional) – the corresponding sort directions for each sort column, default is empty. In the absence of explicit sort directions, data will be sorted in the ascending order.

Returns:

self

std_by(by=[])[source]#

Add a std-by aggregation to the query.

Parameters:: by (List[str]) – the group-by column names
Returns:: self

sum_by(by=[])[source]#

Add a sum-by aggregation to the query.

Parameters:: by (List[str]) – the group-by column names
Returns:: self

tail(num_rows)[source]#

Add a tail operation to the query.

Parameters:: num_rows (int) – the number of rows at the end of table
Returns:: self

tail_by(num_rows, by)[source]#

Add a tail-by operation to the query.

Parameters:

num_rows (int) – the number of rows at the end of each group
by (List[str]) – the group-by column names

Returns:

self

ungroup(cols=[], null_fill=True)[source]#

Add an ungroup operation to the query.

Parameters:

cols (List[str], optional) – the names of the array columns, if empty, all array columns will be ungrouped, default is empty
null_fill (bool, optional) – indicates whether null should be used to fill missing cells, default is True

Returns:

self

update(formulas)[source]#

Add an update operation to the query.

Parameters:: formulas (List[str]) – the column formulas
Returns:: self

update_by(ops, by)[source]#

Add an update-by operation to the query.

Parameters:

ops (List[UpdateByOperation]) – the UpdateByOperations to be applied
by (List[str]) – the group-by column names

Returns:

self

update_view(formulas)[source]#

Add an update-view operation to the query.

Parameters:: formulas (List[str]) – the column formulas
Returns:: self

var_by(by=[])[source]#

Add a var-by aggregation to the query.

Parameters:: by (List[str], optional) – the group-by column names, default is empty
Returns:: self

view(formulas)[source]#

Add a view operation to the query.

Parameters:: formulas (List[str]) – the column formulas
Returns:: self

where(filters)[source]#

Add a filter operation to the query.

Parameters:: filters (List[str]) – a list of filter condition expressions
Returns:: self