|
| 1 | +<REFENTRY ID="SQL-EXPLAIN"> |
| 2 | +<REFMETA> |
| 3 | +<REFENTRYTITLE> |
| 4 | +EXPLAIN |
| 5 | +</REFENTRYTITLE> |
| 6 | +<REFMISCINFO>SQL - Language Statements</REFMISCINFO> |
| 7 | +</REFMETA> |
| 8 | +<REFNAMEDIV> |
| 9 | +<REFNAME> |
| 10 | +EXPLAIN |
| 11 | +</REFNAME> |
| 12 | +<REFPURPOSE> |
| 13 | +Shows statement execution details. |
| 14 | +</REFPURPOSE> |
| 15 | + |
| 16 | +<REFSYNOPSISDIV> |
| 17 | +<REFSYNOPSISDIVINFO> |
| 18 | +<DATE>1998-09-01</DATE> |
| 19 | +</REFSYNOPSISDIVINFO> |
| 20 | +<SYNOPSIS> |
| 21 | +EXPLAIN [ VERBOSE ] <REPLACEABLE CLASS="PARAMETER">query</REPLACEABLE> |
| 22 | +</SYNOPSIS> |
| 23 | + |
| 24 | +<REFSECT2 ID="R2-SQL-EXPLAIN-1"> |
| 25 | +<REFSECT2INFO> |
| 26 | +<DATE>1998-09-01</DATE> |
| 27 | +</REFSECT2INFO> |
| 28 | +<TITLE> |
| 29 | +Inputs |
| 30 | +</TITLE> |
| 31 | +<PARA> |
| 32 | + |
| 33 | +<VARIABLELIST> |
| 34 | +<VARLISTENTRY> |
| 35 | +<TERM> |
| 36 | +VERBOSE |
| 37 | +</TERM> |
| 38 | +<LISTITEM> |
| 39 | +<PARA> |
| 40 | +Flag to show detailed query plan. |
| 41 | + |
| 42 | +<VARLISTENTRY> |
| 43 | +<TERM> |
| 44 | +<REPLACEABLE CLASS="PARAMETER">query</REPLACEABLE> |
| 45 | +</TERM> |
| 46 | +<LISTITEM> |
| 47 | +<PARA> |
| 48 | +Any <REPLACEABLE CLASS="PARAMETER">query</REPLACEABLE>. |
| 49 | + |
| 50 | +</VARIABLELIST> |
| 51 | + |
| 52 | +</REFSECT2> |
| 53 | + |
| 54 | +<REFSECT2 ID="R2-SQL-EXPLAIN-2"> |
| 55 | +<REFSECT2INFO> |
| 56 | +<DATE>1998-04-15</DATE> |
| 57 | +</REFSECT2INFO> |
| 58 | +<TITLE> |
| 59 | +Outputs |
| 60 | +</TITLE> |
| 61 | +<PARA> |
| 62 | + |
| 63 | +<VARIABLELIST> |
| 64 | +<VARLISTENTRY> |
| 65 | +<TERM> |
| 66 | +NOTICE: QUERY PLAN: |
| 67 | +</TERM> |
| 68 | +<LISTITEM> |
| 69 | +<PARA> |
| 70 | +Explicit query plan from the <productname>Postgres</productname> backend. |
| 71 | + |
| 72 | +<VARLISTENTRY> |
| 73 | +<TERM> |
| 74 | +EXPLAIN |
| 75 | +</TERM> |
| 76 | +<LISTITEM> |
| 77 | +<PARA> |
| 78 | +Flag sent after query plan is shown. |
| 79 | + |
| 80 | +</VARIABLELIST> |
| 81 | + |
| 82 | +</REFSECT2> |
| 83 | +</REFSYNOPSISDIV> |
| 84 | + |
| 85 | +<REFSECT1 ID="R1-SQL-EXPLAIN-1"> |
| 86 | +<REFSECT1INFO> |
| 87 | +<DATE>1998-04-15</DATE> |
| 88 | +</REFSECT1INFO> |
| 89 | +<TITLE> |
| 90 | +Description |
| 91 | +</TITLE> |
| 92 | +<PARA> |
| 93 | + This command outputs details about the supplied query. |
| 94 | + The default output is the computed query cost. |
| 95 | + VERBOSE displays the full query plan and cost. |
| 96 | + |
| 97 | +<REFSECT2 ID="R2-SQL-EXPLAIN-3"> |
| 98 | +<REFSECT2INFO> |
| 99 | +<DATE>1998-04-15</DATE> |
| 100 | +</REFSECT2INFO> |
| 101 | +<TITLE> |
| 102 | +Notes |
| 103 | +</TITLE> |
| 104 | +<PARA> |
| 105 | + |
| 106 | +</REFSECT2> |
| 107 | + |
| 108 | +<REFSECT1 ID="R1-SQL-EXPLAIN-2"> |
| 109 | +<TITLE> |
| 110 | +Usage |
| 111 | +</TITLE> |
| 112 | +<PARA> |
| 113 | +To show a query plan for a simple query: |
| 114 | + |
| 115 | +<ProgramListing> |
| 116 | +postgres=> explain select * from foo; |
| 117 | +NOTICE: QUERY PLAN: |
| 118 | + |
| 119 | +Seq Scan on foo (cost=0.00 size=0 width=4) |
| 120 | + |
| 121 | +EXPLAIN |
| 122 | +</ProgramListing> |
| 123 | + |
| 124 | +</REFSECT1> |
| 125 | + |
| 126 | +<REFSECT1 ID="R1-SQL-EXPLAIN-3"> |
| 127 | +<TITLE> |
| 128 | +Compatibility |
| 129 | +</TITLE> |
| 130 | +<PARA> |
| 131 | +</PARA> |
| 132 | + |
| 133 | +<REFSECT2 ID="R2-SQL-EXPLAIN-4"> |
| 134 | +<REFSECT2INFO> |
| 135 | +<DATE>1998-09-01</DATE> |
| 136 | +</REFSECT2INFO> |
| 137 | +<TITLE> |
| 138 | +SQL92 |
| 139 | +</TITLE> |
| 140 | +<PARA> |
| 141 | + There is no EXPLAIN statement defined in SQL92. |
| 142 | +</REFENTRY> |
| 143 | + |
| 144 | +<!-- |
| 145 | +<REPLACEABLE CLASS="PARAMETER"> |
| 146 | +</REPLACEABLE> |
| 147 | +<ReturnValue></ReturnValue> |
| 148 | +<PARA> |
| 149 | +</PARA> |
| 150 | +<VARIABLELIST> |
| 151 | +<VARLISTENTRY> |
| 152 | +<TERM>• |
| 153 | +</TERM> |
| 154 | +<LISTITEM> |
| 155 | +<PARA> |
| 156 | +</PARA> |
| 157 | +</LISTITEM> |
| 158 | +</VARLISTENTRY> |
| 159 | +</VARIABLELIST> |
| 160 | +<PARA> |
| 161 | +</PARA> |
| 162 | +--> |