杂七杂八的，随手记录。

gp shared snapshot

yc 发布于 0001-01-01

Table of Contents

1 DtaStrutor

本文为摘录(或转载)，侵删，原文为： ../../../Work/pg_gpdb/src/backend/utils/time/sharedsnapshot.c

在 Greenplum 中，作为切片计划的一部分，许多 PostgreSQL 进程（qExecs，QE）在单个段数据库上运行，作为同一用户 SQL 语句的一部分。属于特定用户在特定段数据库上的所有 qExecs 需要具有一致的可见性。为此，使用了一种称为“共享本地快照”（Shared Local Snapshot）的思想。共享内存数据结构 SharedSnapshotSlot 在特定数据库实例上的会话的统一流程（gang processes）之间共享会话和事务信息。这些流程被称为 SegMate 进程组。

gpcheckcat

yc 发布于 0001-01-01

Table of Contents

1 概述
2 pg_class
3 namespace
4 unique_index_violation
5 duplicate

1 概述

GP 提供了 gpcheckcat 用于在集群内检查系统表。

Table 1: gpcheckcat

| 检查项 || 描述 || Utility 模式 || 复合查询 || 错误等级 | |———————|————————————————————————-|————|——|——| | pg_class || Check pg_class entry that does not have any correspond pg_attribute entry || Y || N || NOREPAIR | | namespace || Check for schemas with a missing schema definition || Y || N || NOREPAIR | | unique_index_violation || Check for violated unique indexes || N || Y || NOREPAIR | | duplicate || Check for duplicate entries || N || Y || | | missing_extraneous || Cross consistency check for missing or extraneous entries || N || Y || | | inconsistent || Cross consistency check for coordinator segment inconsistency || N || || | | foreign_key || Check foreign keys || N || || | | || || || || |

gpdb cdb

yc 发布于 0001-01-01

Table of Contents

1 Data structures
- 1.1 Slice Table
2 PostgresMain
- 2.1 Call graph (QE):
- 2.2 QD
3 Receiver
4 Sender

1 Data structures

1.1 Slice Table

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@startuml
class SliceTable {
+ NodeTag type
+ int localSlice
+ int numSlices
+ ExecSlice slices
+ bool hasMotions
+ int instrument_options
+ uint32 ic_instance_id
}

note right of SliceTable::localSlice
Index of the slice to execute
end note

note right of SliceTable::slices
Array of slices, indexed by SliceIndex
end note


note right of SliceTable::hasMotions
Are there any Motion nodes anywhere in the plan?
end note


class ExecSlice {
+ int sliceIndex
+ int rootIndex
+ int parentIndex
+ int planNumSegments
+ List children
+ GangType gangType
+ List segments
+ struct primaryGang
+ List primaryProcesses
+ Bitmapset processesMap
}

note right of ExecSlice::primaryProcesses
A list of CDBProcess nodes corresponding to the worker
processes allocated to implement this plan slice.
end note

note right of ExecSlice::processesMap
A bitmap to identify which QE should execute this slice
end note

SliceTable o-- ExecSlice

class Gang {
+ GangType type
+ int size
+ struct db_descriptors
+ bool allocated
}

note right of Gang::db_descriptors
Array of QEs/segDBs that make up this gang.
Sorted by segment index.
end note


ExecSlice *-- Gang

class CdbProcess {
+ NodeTag type
+ char listenerAddr
+ int listenerPort
+ int pid
+ int contentid
+ int dbid
}

ExecSlice o-- CdbProcess



class SegmentDatabaseDescriptor {
+ struct segment_database_info
+ int segindex
+ int conn
+ int motionListener
+ int backendPid
+ char whoami
+ int isWriter
+ int identifier
}

Gang o-- SegmentDatabaseDescriptor



class CdbComponentDatabases {
+ CdbComponentDatabaseInfo segment_db_info
+ int total_segment_dbs
+ CdbComponentDatabaseInfo entry_db_info
+ int total_entry_dbs
+ int total_segments
+ int fts_version
+ int expand_version
+ int numActiveQEs
+ int numIdleQEs
+ int qeCounter
+ List freeCounterList
}

note right of CdbComponentDatabaseInfo::segment_db_info
array of  SegmentDatabaseInfo for segment databases
end note

note right of CdbComponentDatabaseInfo::entry_db_info
array of  SegmentDatabaseInfo for entry databases
end note


class CdbComponentDatabaseInfo {
+ struct config
+ CdbComponentDatabases cdbs
+ int hostSegs
+ List freelist
+ int numIdleQEs
+ int numActiveQEs
}

note right of CdbComponentDatabaseInfo::cdbs
point to owners
end note

CdbComponentDatabases o-- CdbComponentDatabaseInfo



class GpSegConfigEntry {
+ int dbid
+ int segindex
+ char role
+ char preferred_role
+ char mode
+ char status
+ int port
+ char hostname
+ char address
+ char datadir
+ char hostip
+ char hostaddrs
}

CdbComponentDatabaseInfo o-- GpSegConfigEntry

SegmentDatabaseDescriptor o-- CdbComponentDatabaseInfo

@enduml

gpdb memory control

yc 发布于 0001-01-01

Table of Contents

1 TODO VMem
2 Resource Group Control
- 2.1 Bypass
- 2.2 Fixed Mem
- 2.3 Memory Limit

TODO 1 VMem

2 Resource Group Control

ResourceGroupGetQueryMemoryLimit(void) 用于获取内存限制的绝对大小（非百分比）

2.1 Bypass

绕开资源限制模式

Enabled when:

gp_resource_group_bypass is true: guc_gp.c

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{
    {"gp_resource_group_bypass", PGC_USERSET, RESOURCES,
        gettext_noop("If the value is true, the query in this session will not be limited by resource group."),
        NULL
    },
    &gp_resource_group_bypass,
    false,
    check_gp_resource_group_bypass, NULL, NULL
}

Or command is one of:

GPDB: Configuring Your Systems

yc 发布于 0001-01-01

Table of Contents

1 IP Fragmentation Settings
2 Networking

本文为摘录(或转载)，侵删，原文为： https://docs.vmware.com/en/VMware-Tanzu-Greenplum/6/greenplum-database/GUID-install_guide-prep_os.html

1 IP Fragmentation Settings

IP Fragmentation Settings

When the Greenplum Database interconnect uses UDP (the default), the network interface card controls IP packet fragmentation and reassemblies.

If the UDP message size is larger than the size of the maximum transmission unit (MTU) of a network, the IP layer fragments the message. (Refer to Networking later in this topic for more information about MTU sizes for Greenplum Database.) The receiver must store the fragments in a buffer before it can reorganize and reassemble the message.

Greenplum 部署最佳实践: 网络篇

yc 发布于 0001-01-01

Table of Contents

1 使用高速硬件，降低节点间的延迟
2 尽量降低网络中断的次数。
3 尽量提高每一个数据包的有效载荷

本文为摘录(或转载)，侵删，原文为： attachments/pdf/a/cn.greenplum.org-Greenplum部署最佳实践-网络篇.pdf