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Merge pull request #45451 from evillique/default_granularity

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Add default GRANULARITY argument for secondary indexes
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robot-ch-test-poll4 2023-01-20 17:46:21 +01:00 committed by GitHub
commit 2066581d8f
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4 changed files with 16 additions and 9 deletions
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8
docs/en/engines/table-engines/mergetree-family/mergetree.md
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@ -40,8 +40,8 @@ CREATE TABLE [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster]
name1 [type1] [DEFAULT|MATERIALIZED|ALIAS expr1] [TTL expr1],
name2 [type2] [DEFAULT|MATERIALIZED|ALIAS expr2] [TTL expr2],
...
INDEX index_name1 expr1 TYPE type1(...) GRANULARITY value1,
INDEX index_name2 expr2 TYPE type2(...) GRANULARITY value2,
INDEX index_name1 expr1 TYPE type1(...) [GRANULARITY value1],
INDEX index_name2 expr2 TYPE type2(...) [GRANULARITY value2],
...
PROJECTION projection_name_1 (SELECT <COLUMN LIST EXPR> [GROUP BY] [ORDER BY]),
PROJECTION projection_name_2 (SELECT <COLUMN LIST EXPR> [GROUP BY] [ORDER BY])
@ -359,13 +359,15 @@ ClickHouse uses this logic not only for days of the month sequences, but for any
The index declaration is in the columns section of the `CREATE` query.
``` sql
INDEX index_name expr TYPE type(...) GRANULARITY granularity_value
INDEX index_name expr TYPE type(...) [GRANULARITY granularity_value]
```
For tables from the `*MergeTree` family, data skipping indices can be specified.
These indices aggregate some information about the specified expression on blocks, which consist of `granularity_value` granules (the size of the granule is specified using the `index_granularity` setting in the table engine). Then these aggregates are used in `SELECT` queries for reducing the amount of data to read from the disk by skipping big blocks of data where the `where` query cannot be satisfied.
The `GRANULARITY` clause can be omitted, the default value of `granularity_value` is 1.
**Example**
``` sql

12
src/Parsers/ParserCreateQuery.cpp
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@ -131,15 +131,15 @@ bool ParserIndexDeclaration::parseImpl(Pos & pos, ASTPtr & node, Expected & expe
if (!data_type_p.parse(pos, type, expected))
return false;
if (!s_granularity.ignore(pos, expected))
return false;
if (!granularity_p.parse(pos, granularity, expected))
return false;
if (s_granularity.ignore(pos, expected))
{
if (!granularity_p.parse(pos, granularity, expected))
return false;
}
auto index = std::make_shared<ASTIndexDeclaration>();
index->name = name->as<ASTIdentifier &>().name();
index->granularity = granularity->as<ASTLiteral &>().value.safeGet<UInt64>();
index->granularity = granularity ? granularity->as<ASTLiteral &>().value.safeGet<UInt64>() : 1;
index->set(index->expr, expr);
index->set(index->type, type);
node = index;

1
tests/queries/0_stateless/02534_default_granularity.reference Normal file
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@ -0,0 +1 @@
CREATE TABLE default.users_02534\n(\n `id` Int16,\n `name` String,\n INDEX bf_idx name TYPE minmax GRANULARITY 1\n)\nENGINE = MergeTree\nORDER BY id\nSETTINGS index_granularity = 8192

4
tests/queries/0_stateless/02534_default_granularity.sql Normal file
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@ -0,0 +1,4 @@
DROP TABLE IF EXISTS users_02534;
CREATE TABLE users_02534 (id Int16, name String, INDEX bf_idx(name) TYPE minmax) ENGINE=MergeTree ORDER BY id;
SHOW CREATE TABLE users_02534;
DROP TABLE users_02534;