Firebird-5-Release-Notes | More Cursor-Related Details In The Plan Output

SQL and PSQL profiler

Adriano dos Santos Fernandes

Tracker ticket: #7086

The profiler allows users to measure performance cost of SQL and PSQL code.It’s implemented with a system package in the engine passing data to a profiler plugin.

This documentation treats the engine and plugin parts as a single thing, in the way the default profiler (Default_Profiler) is going to be used.

The RDB$PROFILER package can profile execution of PSQL code, collecting statistics of how many times each line was executed along with its minimum, maximum and accumulated execution times (with nanoseconds precision), as well as open and fetch statistics of implicit and explicit SQL cursors.

To collect profile data, a user must first start a profile session with RDB$PROFILER.START_SESSION.This function returns a profile session ID which is later stored in the profiler snapshot tables to be queried and analyzed by the user.A profiler session may be local (same attachment) or remote (another attachment).

Remote profiling just forwards commands to the remote attachment.So, it’s possible that a client profiles multiple attachments simultaneously.It’s also possible that a locally or remotely started profile session have commands issued by another attachment.

Remotely issued commands require that the target attachment is in an idle state, i.e. not executing others requests.When the target attachment is not idle, the call blocks waiting for that state.

If the remote attachment is from a different user, the calling user must have the system privilege PROFILE_ANY_ATTACHMENT.

After a session is started, PSQL and SQL statements statistics are collected in memory.A profile session collects data only of statements executed in the same attachment associated with the session.Data is aggregated and stored per requests (i.e. a statement execution).When querying snapshot tables, the user may do extra aggregation per statement, or use the auxiliary views that do that automatically.

A session may be paused to temporarily disable statistics collecting.It may be resumed later to return statistics collection in the same session.

A new session may be started when a session is already active.In that case, it has the same semantics of finishing the current session with RDB$PROFILER.FINISH_SESSION(FALSE), so snapshots tables are not updated.

To analyze the collected data, the user must flush the data to the snapshot tables, which can be done by finishing or pausing a session (with FLUSH parameter set to TRUE), or calling RDB$PROFILER.FLUSH.Data is flushed using an autonomous transaction (a transaction started and finished for the specific purpose of profiler data update).

Below is a sample profile session and queries for data analysis.

Preparation — create table and routines that will be analyzed

create table tab (
    id integer not null,
    val integer not null
);

set term !;

create or alter function mult(p1 integer, p2 integer) returns integer
as
begin
    return p1 * p2;
end!

create or alter procedure ins
as
    declare n integer = 1;
begin
    while (n <= 1000)
    do
    begin
        if (mod(n, 2) = 1) then
            insert into tab values (:n, mult(:n, 2));
        n = n + 1;
    end
end!

set term ;!

Start profiling

select rdb$profiler.start_session('Profile Session 1') from rdb$database;

set term !;

execute block
as
begin
    execute procedure ins;
    delete from tab;
end!

set term ;!

execute procedure rdb$profiler.finish_session(true);

execute procedure ins;

select rdb$profiler.start_session('Profile Session 2') from rdb$database;

select mod(id, 5),
       sum(val)
  from tab
  where id <= 50
  group by mod(id, 5)
  order by sum(val);

execute procedure rdb$profiler.finish_session(true);

Data analysis

set transaction read committed;

select * from plg$prof_sessions;

select * from plg$prof_psql_stats_view;

select * from plg$prof_record_source_stats_view;

select preq.*
  from plg$prof_requests preq
  join plg$prof_sessions pses
    on pses.profile_id = preq.profile_id and
       pses.description = 'Profile Session 1';

select pstat.*
  from plg$prof_psql_stats pstat
  join plg$prof_sessions pses
    on pses.profile_id = pstat.profile_id and
       pses.description = 'Profile Session 1'
  order by pstat.profile_id,
           pstat.request_id,
           pstat.line_num,
           pstat.column_num;

select pstat.*
  from plg$prof_record_source_stats pstat
  join plg$prof_sessions pses
    on pses.profile_id = pstat.profile_id and
       pses.description = 'Profile Session 2'
  order by pstat.profile_id,
           pstat.request_id,
           pstat.cursor_id,
           pstat.record_source_id;

Package routines

Function `START_SESSION`

RDB$PROFILER.START_SESSION starts a new profiler session, makes it the current session (of the given ATTACHMENT_ID) and returns its identifier.

If FLUSH_INTERVAL is different from NULL, auto-flush is set up in the same way as manually calling RDB$PROFILER.SET_FLUSH_INTERVAL.

If PLUGIN_NAME is NULL (the default), it uses the database configuration DefaultProfilerPlugin.

PLUGIN_OPTIONS are plugin specific options and currently should be NULL for the Default_Profiler plugin.

Input parameters

DESCRIPTION type VARCHAR(255) CHARACTER SET UTF8 default NULL
FLUSH_INTERVAL type INTEGER default NULL
ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION
PLUGIN_NAME type VARCHAR(255) CHARACTER SET UTF8 default NULL
PLUGIN_OPTIONS type VARCHAR(255) CHARACTER SET UTF8 default NULL

Return type

BIGINT NOT NULL

Procedure `PAUSE_SESSION`

RDB$PROFILER.PAUSE_SESSION pauses the current profiler session (of the given ATTACHMENT_ID), so the next executed statements statistics are not collected.

If FLUSH is TRUE, the snapshot tables are updated with data up to the current moment, otherwise data remains only in memory for later update.

Calling RDB$PROFILER.PAUSE_SESSION(TRUE) has the same semantics as calling RDB$PROFILER.PAUSE_SESSION(FALSE) followed by RDB$PROFILER.FLUSH (using the same ATTACHMENT_ID).

Input parameters

FLUSH type BOOLEAN NOT NULL default FALSE
ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION

Procedure `RESUME_SESSION`

RDB$PROFILER.RESUME_SESSION resumes the current profiler session (of the given ATTACHMENT_ID), if it was paused, so the next executed statements statistics are collected again.

Input parameter

ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION

Procedure `FINISH_SESSION`

RDB$PROFILER.FINISH_SESSION finishes the current profiler session (of the given ATTACHMENT_ID).

If FLUSH is TRUE, the snapshot tables are updated with data of the finished session (and old finished sessions not yet present in the snapshot), otherwise data remains only in memory for later update.

Calling RDB$PROFILER.FINISH_SESSION(TRUE) has the same semantics of calling RDB$PROFILER.FINISH_SESSION(FALSE) followed by RDB$PROFILER.FLUSH (using the same ATTACHMENT_ID).

Input parameters

FLUSH type BOOLEAN NOT NULL default TRUE
ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION

Procedure `CANCEL_SESSION`

RDB$PROFILER.CANCEL_SESSION cancels the current profiler session (of the given ATTACHMENT_ID).

All session data present in the profiler plugin is discarded and will not be flushed.

Data already flushed is not deleted automatically.

Input parameter

ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION

Procedure `DISCARD`

RDB$PROFILER.DISCARD removes all sessions (of the given ATTACHMENT_ID) from memory, without flushing them.

If there is an active session, it is cancelled.

Input parameter

ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION

Procedure `FLUSH`

RDB$PROFILER.FLUSH updates the snapshot tables with data from the profile sessions (of the given ATTACHMENT_ID) in memory.

After flushing, the data is stored in tables PLG$PROF_SESSIONS, PLG$PROF_STATEMENTS, PLG$PROF_RECORD_SOURCES, PLG$PROF_REQUESTS, PLG$PROF_PSQL_STATS and PLG$PROF_RECORD_SOURCE_STATS and may be read and analyzed by the user.

Data is updated using an autonomous transaction, so if the procedure is called in a snapshot transaction, data will not be directly readable in the same transaction.

Once flush happens, finished sessions are removed from memory.

Input parameter

ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION

Procedure `SET_FLUSH_INTERVAL`

RDB$PROFILER.SET_FLUSH_INTERVAL turns periodic auto-flush on (when FLUSH_INTERVAL is greater than 0) or off (when FLUSH_INTERVAL is equal to 0).

FLUSH_INTERVAL is interpreted as number of seconds.

Input parameters

FLUSH_INTERVAL type INTEGER NOT NULL
ATTACHMENT_ID type BIGINT NOT NULL default CURRENT_CONNECTION

Snapshot tables

Snapshot tables (as well views and sequence) are automatically created in the first usage of the profiler.They are owned by the database owner, with read/write permissions for PUBLIC.

When a session is deleted, the related data in other profiler snapshot tables are automatically deleted too through foreign keys with DELETE CASCADE option.

Below is the list of tables that stores profile data.

Table `PLG$PROF_SESSIONS`

`PROFILE_ID type BIGINT`	Profile session ID
`ATTACHMENT_ID type BIGINT`	Attachment ID
`USER_NAME type CHAR(63) CHARACTER SET UTF8`	Username
`DESCRIPTION type VARCHAR(255) CHARACTER SET UTF8`	Description passed in `RDB$PROFILER.START_SESSION`
`START_TIMESTAMP type TIMESTAMP WITH TIME ZONE`	Moment the profile session was started
`FINISH_TIMESTAMP type TIMESTAMP WITH TIME ZONE`	Moment the profile session was finished (NULL when not finished)
Primary key	`PROFILE_ID`

Table `PLG$PROF_STATEMENTS`

`PROFILE_ID type BIGINT`	Profile session ID
`STATEMENT_ID type BIGINT`	Statement ID
`PARENT_STATEMENT_ID type BIGINT`	Parent statement ID — related to sub routines
`STATEMENT_TYPE type VARCHAR(20) CHARACTER SET UTF8`	BLOCK, FUNCTION, PROCEDURE or TRIGGER
`PACKAGE_NAME type CHAR(63) CHARACTER SET UTF8`	Package of FUNCTION or PROCEDURE
`ROUTINE_NAME type CHAR(63) CHARACTER SET UTF8`	Routine name of FUNCTION, PROCEDURE or TRIGGER
`SQL_TEXT type BLOB SUB_TYPE TEXT CHARACTER SET UTF8`	SQL text for BLOCK
Primary key	`PROFILE_ID`, `STATEMENT_ID`

Table `PLG$PROF_CURSORS`

`PROFILE_ID type BIGINT`	Profile session ID
`STATEMENT_ID type BIGINT`	Statement ID
`CURSOR_ID type INTEGER`	Cursor ID
`NAME type CHAR(63) CHARACTER SET UTF8`	Name of explicit cursor
`LINE_NUM type INTEGER`	Line number of the cursor
`COLUMN_NUM type INTEGER`	Column number of the cursor
Primary key	`PROFILE_ID`, `STATEMENT_ID`, `CURSOR_ID`

Table `PLG$PROF_RECORD_SOURCES`

`PROFILE_ID type BIGINT`	Profile session ID
`STATEMENT_ID type BIGINT`	Statement ID
`CURSOR_ID type INTEGER`	Cursor ID
`RECORD_SOURCE_ID type INTEGER`	Record source ID
`PARENT_RECORD_SOURCE_ID type INTEGER`	Parent record source ID
`LEVEL`	Indentation level for the record source
`ACCESS_PATH type BLOB SUB_TYPE TEXT CHARACTER SET UTF8`	Access path for the record source
Primary key	`PROFILE_ID`, `STATEMENT_ID`, `CURSOR_ID`, `RECORD_SOURCE_ID`

Table `PLG$PROF_REQUESTS`

`PROFILE_ID type BIGINT`	Profile session ID
`STATEMENT_ID type BIGINT`	Statement ID
`REQUEST_ID type BIGINT`	Request ID
`CALLER_STATEMENT_ID type BIGINT`	Caller statement ID
`CALLER_REQUEST_ID type BIGINT`	Caller request ID
`START_TIMESTAMP type TIMESTAMP WITH TIME ZONE`	Moment this request was first gathered profile data
`FINISH_TIMESTAMP type TIMESTAMP WITH TIME ZONE`	Moment this request was finished
`TOTAL_ELAPSED_TIME type BIGINT`	Accumulated elapsed time (in nanoseconds) of the request
Primary key	`PROFILE_ID`, `REQUEST_ID`

Table `PLG$PROF_PSQL_STATS`

`PROFILE_ID type BIGINT`	Profile session ID
`STATEMENT_ID type BIGINT`	Statement ID
`REQUEST_ID type BIGINT`	Request ID
`LINE_NUM type INTEGER`	Line number of the statement
`COLUMN_NUM type INTEGER`	Column number of the statement
`COUNTER type BIGINT`	Number of executed times of the line/column
`MIN_ELAPSED_TIME type BIGINT`	Minimal elapsed time (in nanoseconds) of a line/column execution
`MAX_ELAPSED_TIME type BIGINT`	Maximum elapsed time (in nanoseconds) of a line/column execution
`TOTAL_ELAPSED_TIME type BIGINT`	Accumulated elapsed time (in nanoseconds) of the line/column executions
Primary key	`PROFILE_ID`, `REQUEST_ID`, `LINE_NUM`, `COLUMN_NUM`

Table `PLG$PROF_RECORD_SOURCE_STATS`

`PROFILE_ID type BIGINT`	Profile session ID
`STATEMENT_ID type BIGINT`	Statement ID
`REQUEST_ID type BIGINT`	Request ID
`CURSOR_ID type INTEGER`	Cursor ID
RECORD_SOURCE_ID type `INTEGER	Record source ID
`OPEN_COUNTER type BIGINT`	Number of open times of the record source
`OPEN_MIN_ELAPSED_TIME type BIGINT`	Minimal elapsed time (in nanoseconds) of a record source open
`OPEN_MAX_ELAPSED_TIME type BIGINT`	Maximum elapsed time (in nanoseconds) of a record source open
`OPEN_TOTAL_ELAPSED_TIME type BIGINT`	Accumulated elapsed time (in nanoseconds) of the record source openings
`FETCH_COUNTER type BIGINT`	Number of fetch times of the record source
`FETCH_MIN_ELAPSED_TIME type BIGINT`	Minimal elapsed time (in nanoseconds) of a record source fetch
`FETCH_MAX_ELAPSED_TIME type BIGINT`	Maximum elapsed time (in nanoseconds) of a record source fetch
`FETCH_TOTAL_ELAPSED_TIME type BIGINT`	Accumulated elapsed time (in nanoseconds) of the record source fetches
Primary key	`PROFILE_ID`, `REQUEST_ID`, `CURSOR_ID`, `RECORD_SOURCE_ID`

Auxiliary views

These views help profile data extraction aggregated at statement level.

They should be the preferred way to analyze the collected data.They can also be used together with the tables to get additional data not present on the views.

After hotspots are found, one can drill down in the data at the request level through the tables.

View `PLG$PROF_STATEMENT_STATS_VIEW`

select req.profile_id,
       req.statement_id,
       sta.statement_type,
       sta.package_name,
       sta.routine_name,
       sta.parent_statement_id,
       sta_parent.statement_type parent_statement_type,
       sta_parent.routine_name parent_routine_name,
       (select sql_text
          from plg$prof_statements
          where profile_id = req.profile_id and
                statement_id = coalesce(sta.parent_statement_id, req.statement_id)
       ) sql_text,
       count(*) counter,
       min(req.total_elapsed_time) min_elapsed_time,
       max(req.total_elapsed_time) max_elapsed_time,
       cast(sum(req.total_elapsed_time) as bigint) total_elapsed_time,
       cast(sum(req.total_elapsed_time) / count(*) as bigint) avg_elapsed_time
  from plg$prof_requests req
  join plg$prof_statements sta
    on sta.profile_id = req.profile_id and
       sta.statement_id = req.statement_id
  left join plg$prof_statements sta_parent
    on sta_parent.profile_id = sta.profile_id and
       sta_parent.statement_id = sta.parent_statement_id
  group by req.profile_id,
           req.statement_id,
           sta.statement_type,
           sta.package_name,
           sta.routine_name,
           sta.parent_statement_id,
           sta_parent.statement_type,
           sta_parent.routine_name
  order by sum(req.total_elapsed_time) desc

View `PLG$PROF_PSQL_STATS_VIEW`

select pstat.profile_id,
       pstat.statement_id,
       sta.statement_type,
       sta.package_name,
       sta.routine_name,
       sta.parent_statement_id,
       sta_parent.statement_type parent_statement_type,
       sta_parent.routine_name parent_routine_name,
       (select sql_text
          from plg$prof_statements
          where profile_id = pstat.profile_id and
                statement_id = coalesce(sta.parent_statement_id, pstat.statement_id)
       ) sql_text,
       pstat.line_num,
       pstat.column_num,
       cast(sum(pstat.counter) as bigint) counter,
       min(pstat.min_elapsed_time) min_elapsed_time,
       max(pstat.max_elapsed_time) max_elapsed_time,
       cast(sum(pstat.total_elapsed_time) as bigint) total_elapsed_time,
       cast(sum(pstat.total_elapsed_time) / nullif(sum(pstat.counter), 0) as bigint) avg_elapsed_time
  from plg$prof_psql_stats pstat
  join plg$prof_statements sta
    on sta.profile_id = pstat.profile_id and
       sta.statement_id = pstat.statement_id
  left join plg$prof_statements sta_parent
    on sta_parent.profile_id = sta.profile_id and
       sta_parent.statement_id = sta.parent_statement_id
  group by pstat.profile_id,
           pstat.statement_id,
           sta.statement_type,
           sta.package_name,
           sta.routine_name,
           sta.parent_statement_id,
           sta_parent.statement_type,
           sta_parent.routine_name,
           pstat.line_num,
           pstat.column_num
  order by sum(pstat.total_elapsed_time) desc

View `PLG$PROF_RECORD_SOURCE_STATS_VIEW`

select rstat.profile_id,
       rstat.statement_id,
       sta.statement_type,
       sta.package_name,
       sta.routine_name,
       sta.parent_statement_id,
       sta_parent.statement_type parent_statement_type,
       sta_parent.routine_name parent_routine_name,
       (select sql_text
          from plg$prof_statements
          where profile_id = rstat.profile_id and
                statement_id = coalesce(sta.parent_statement_id, rstat.statement_id)
       ) sql_text,
       rstat.cursor_id,
       cur.name cursor_name,
       cur.line_num cursor_line_num,
       cur.column_num cursor_column_num,
       rstat.record_source_id,
       recsrc.parent_record_source_id,
       recsrc.level,
       recsrc.access_path,
       cast(sum(rstat.open_counter) as bigint) open_counter,
       min(rstat.open_min_elapsed_time) open_min_elapsed_time,
       max(rstat.open_max_elapsed_time) open_max_elapsed_time,
       cast(sum(rstat.open_total_elapsed_time) as bigint) open_total_elapsed_time,
       cast(sum(rstat.open_total_elapsed_time) / nullif(sum(rstat.open_counter), 0) as bigint) open_avg_elapsed_time,
       cast(sum(rstat.fetch_counter) as bigint) fetch_counter,
       min(rstat.fetch_min_elapsed_time) fetch_min_elapsed_time,
       max(rstat.fetch_max_elapsed_time) fetch_max_elapsed_time,
       cast(sum(rstat.fetch_total_elapsed_time) as bigint) fetch_total_elapsed_time,
       cast(sum(rstat.fetch_total_elapsed_time) / nullif(sum(rstat.fetch_counter), 0) as bigint) fetch_avg_elapsed_time,
       cast(coalesce(sum(rstat.open_total_elapsed_time), 0) + coalesce(sum(rstat.fetch_total_elapsed_time), 0) as bigint) open_fetch_total_elapsed_time
  from plg$prof_record_source_stats rstat
  join plg$prof_cursors cur
    on cur.profile_id = rstat.profile_id and
       cur.statement_id = rstat.statement_id and
       cur.cursor_id = rstat.cursor_id
  join plg$prof_record_sources recsrc
    on recsrc.profile_id = rstat.profile_id and
       recsrc.statement_id = rstat.statement_id and
       recsrc.cursor_id = rstat.cursor_id and
       recsrc.record_source_id = rstat.record_source_id
  join plg$prof_statements sta
    on sta.profile_id = rstat.profile_id and
       sta.statement_id = rstat.statement_id
  left join plg$prof_statements sta_parent
    on sta_parent.profile_id = sta.profile_id and
       sta_parent.statement_id = sta.parent_statement_id
  group by rstat.profile_id,
           rstat.statement_id,
           sta.statement_type,
           sta.package_name,
           sta.routine_name,
           sta.parent_statement_id,
           sta_parent.statement_type,
           sta_parent.routine_name,
           rstat.cursor_id,
           cur.name,
           cur.line_num,
           cur.column_num,
           rstat.record_source_id,
           recsrc.parent_record_source_id,
           recsrc.level,
           recsrc.access_path
  order by coalesce(sum(rstat.open_total_elapsed_time), 0) + coalesce(sum(rstat.fetch_total_elapsed_time), 0) desc

`RDB$BLOB_UTIL` package

Adriano dos Santos Fernandes

Tracker ticket: #281

This package provides procedures and functions to manipulate BLOBs in a way that standard Firebird functions, like BLOB_APPEND and SUBSTRING, cannot do or are very slow.

These routines operate on binary data directly, even for text BLOBs.

Package routines

Function `NEW_BLOB`

RDB$BLOB_UTIL.NEW_BLOB creates a new BLOB SUB_TYPE BINARY.It returns a BLOB suitable for data appending, similar to BLOB_APPEND.

The advantage over BLOB_APPEND is that it’s possible to set custom SEGMENTED and TEMP_STORAGE options.

BLOB_APPEND always creates BLOBs in temporary storage, which may not always be the best approach if the created BLOB is going to be stored in a permanent table, as this will require a copy operation.

The BLOB returned from this function, even when TEMP_STORAGE = FALSE, may be used with BLOB_APPEND for appending data.

Input parameters

SEGMENTED type BOOLEAN NOT NULL
TEMP_STORAGE type BOOLEAN NOT NULL

Return type

BLOB SUB_TYPE BINARY NOT NULL

Function `OPEN_BLOB`

RDB$BLOB_UTIL.OPEN_BLOB opens an existing BLOB for reading.It returns a handle (an integer bound to the transaction) suitable for use with other functions of this package, like SEEK, READ_DATA and CLOSE_HANDLE.

Handles which are not explicitly closed are closed automatically when the transaction ends.

Input parameter

BLOB type BLOB NOT NULL

Return type

INTEGER NOT NULL

Function `IS_WRITABLE`

RDB$BLOB_UTIL.IS_WRITABLE returns TRUE when a BLOB is suitable for data appending using BLOB_APPEND without copying.

Input parameter

BLOB type BLOB NOT NULL

Return type:

BOOLEAN NOT NULL

Function `READ_DATA`

RDB$BLOB_UTIL.READ_DATA reads chunks of data of a BLOB handle opened with RDB$BLOB_UTIL.OPEN_BLOB.When the BLOB is fully read and there is no more data, it returns NULL.

If LENGTH is passed with a positive number, it returns a VARBINARY with its maximum length.

If LENGTH is NULL it returns just a segment of the BLOB with a maximum length of 32765.

Input parameters

HANDLE type INTEGER NOT NULL
LENGTH type INTEGER

Return type

VARBINARY(32765)

Function `SEEK`

RDB$BLOB_UTIL.SEEK sets the position for the next READ_DATA, it returns the new position.

MODE may be 0 (from the start), 1 (from current position) or 2 (from end).

When MODE is 2, OFFSET should be zero or negative.

Input parameters

HANDLE type INTEGER NOT NULL
MODE type INTEGER NOT NULL
OFFSET type INTEGER NOT NULL

Return type

INTEGER NOT NULL

Note	`SEEK` only works on stream blobs.Attempting to seek on a segmented blob results in error “invalid BLOB type for operation”.

Procedure `CANCEL_BLOB`

RDB$BLOB_UTIL.CANCEL_BLOB immediately releases a temporary BLOB, like one created with BLOB_APPEND.

If the same BLOB is used after cancel, an “invalid blob id” error will be raised.

Input parameter

BLOB type BLOB

Procedure `CLOSE_HANDLE`

RDB$BLOB_UTIL.CLOSE_HANDLE closes a BLOB handle opened with RDB$BLOB_UTIL.OPEN_BLOB.

Handles which are not explicitly closed are closed automatically when the transaction ends.

Input parameter

HANDLE type INTEGER NOT NULL

Examples

Create a BLOB in temporary space and return it in EXECUTE BLOCK

execute block returns (b blob)
as
begin
    -- Create a BLOB handle in the temporary space.
    b = rdb$blob_util.new_blob(false, true);

    -- Add chunks of data.
    b = blob_append(b, '12345');
    b = blob_append(b, '67');

    suspend;
end

Open a BLOB and return chunks of it with EXECUTE BLOCK

execute block returns (s varchar(10))
as
    declare b blob = '1234567';
    declare bhandle integer;
begin
    -- Open the BLOB and get a BLOB handle.
    bhandle = rdb$blob_util.open_blob(b);

    -- Get chunks of data as string and return.

    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;

    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;

    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;

    -- Here EOF is found, so it returns NULL.
    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;

    -- Close the BLOB handle.
    execute procedure rdb$blob_util.close_handle(bhandle);
end

Seek in a blob

set term !;

execute block returns (s varchar(10))
as
    declare b blob;
    declare bhandle integer;
begin
    -- Create a stream BLOB handle.
    b = rdb$blob_util.new_blob(false, true);

    -- Add data.
    b = blob_append(b, '0123456789');

    -- Open the BLOB.
    bhandle = rdb$blob_util.open_blob(b);

    -- Seek to 5 since the start.
    rdb$blob_util.seek(bhandle, 0, 5);
    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;

    -- Seek to 2 since the start.
    rdb$blob_util.seek(bhandle, 0, 2);
    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;

    -- Advance 2.
    rdb$blob_util.seek(bhandle, 1, 2);
    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;

    -- Seek to -1 since the end.
    rdb$blob_util.seek(bhandle, 2, -1);
    s = rdb$blob_util.read_data(bhandle, 3);
    suspend;
end!

set term ;!

Check if blobs are writable

create table t(b blob);

set term !;

execute block returns (bool boolean)
as
    declare b blob;
begin
    b = blob_append(null, 'writable');
    bool = rdb$blob_util.is_writable(b);
    suspend;

    insert into t (b) values ('not writable') returning b into b;
    bool = rdb$blob_util.is_writable(b);
    suspend;
end!

set term ;!

More Cursor-Related Details In The Plan Output

More cursor-related details in the plan output

Denser compression of records

docnext count = 3

Compiled statement cache

SQL and PSQL profiler

Package routines

Function `START_SESSION`

Procedure `PAUSE_SESSION`

Procedure `RESUME_SESSION`

Procedure `FINISH_SESSION`

Procedure `CANCEL_SESSION`

Procedure `DISCARD`

Procedure `FLUSH`

Procedure `SET_FLUSH_INTERVAL`

Snapshot tables

Table `PLG$PROF_SESSIONS`

Table `PLG$PROF_STATEMENTS`

Table `PLG$PROF_CURSORS`

Table `PLG$PROF_RECORD_SOURCES`

Table `PLG$PROF_REQUESTS`

Table `PLG$PROF_PSQL_STATS`

Table `PLG$PROF_RECORD_SOURCE_STATS`

Auxiliary views

View `PLG$PROF_STATEMENT_STATS_VIEW`

View `PLG$PROF_PSQL_STATS_VIEW`

View `PLG$PROF_RECORD_SOURCE_STATS_VIEW`

`RDB$BLOB_UTIL` package

Package routines

Function `NEW_BLOB`

Function `OPEN_BLOB`

Function `IS_WRITABLE`

Function `READ_DATA`

Function `SEEK`

Procedure `CANCEL_BLOB`

Procedure `CLOSE_HANDLE`

Examples

More Cursor-Related Details In The Plan Output

More cursor-related details in the plan output

Denser compression of records

docnext count = 3

Compiled statement cache

SQL and PSQL profiler

Package routines

Function START_SESSION

Procedure PAUSE_SESSION

Procedure RESUME_SESSION

Procedure FINISH_SESSION

Procedure CANCEL_SESSION

Procedure DISCARD

Procedure FLUSH

Procedure SET_FLUSH_INTERVAL

Snapshot tables

Table PLG$PROF_SESSIONS

Table PLG$PROF_STATEMENTS

Table PLG$PROF_CURSORS

Table PLG$PROF_RECORD_SOURCES

Table PLG$PROF_REQUESTS

Table PLG$PROF_PSQL_STATS

Table PLG$PROF_RECORD_SOURCE_STATS

Auxiliary views

View PLG$PROF_STATEMENT_STATS_VIEW

View PLG$PROF_PSQL_STATS_VIEW

View PLG$PROF_RECORD_SOURCE_STATS_VIEW

RDB$BLOB_UTIL package

Package routines

Function NEW_BLOB

Function OPEN_BLOB

Function IS_WRITABLE

Function READ_DATA

Function SEEK

Procedure CANCEL_BLOB

Procedure CLOSE_HANDLE

Examples

Function `START_SESSION`

Procedure `PAUSE_SESSION`

Procedure `RESUME_SESSION`

Procedure `FINISH_SESSION`

Procedure `CANCEL_SESSION`

Procedure `DISCARD`

Procedure `FLUSH`

Procedure `SET_FLUSH_INTERVAL`

Table `PLG$PROF_SESSIONS`

Table `PLG$PROF_STATEMENTS`

Table `PLG$PROF_CURSORS`

Table `PLG$PROF_RECORD_SOURCES`

Table `PLG$PROF_REQUESTS`

Table `PLG$PROF_PSQL_STATS`

Table `PLG$PROF_RECORD_SOURCE_STATS`

View `PLG$PROF_STATEMENT_STATS_VIEW`

View `PLG$PROF_PSQL_STATS_VIEW`

View `PLG$PROF_RECORD_SOURCE_STATS_VIEW`

`RDB$BLOB_UTIL` package

Function `NEW_BLOB`

Function `OPEN_BLOB`

Function `IS_WRITABLE`

Function `READ_DATA`

Function `SEEK`

Procedure `CANCEL_BLOB`

Procedure `CLOSE_HANDLE`